WO2025073959A1

WO2025073959A1 - Dielectric heating aerosol-generating device having a temperature determining unit

Info

Publication number: WO2025073959A1
Application number: PCT/EP2024/078047
Authority: WO
Inventors: Oleg Mironov
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2023-10-05
Filing date: 2024-10-04
Publication date: 2025-04-10
Anticipated expiration: 2026-04-05

Abstract

The present invention relates to an aerosol-generating device, and specifically to an aerosol-generating device configured to heat an aerosol-forming substrate by dielectric heating. Provided is a power source; an oscillation circuit including a resonant feedback circuit and a switching unit powered by the power source forming a self-oscillating circuit; a dielectric heating element fed by the oscillation circuit, the dielectric heating element being a capacitor for the resonant feedback circuit, the dielectric heating element being arranged for heating the aerosol-forming substrate by dipole rotation when subjected to an alternating electric field caused by the dielectric heating element; a temperature determining unit for measuring a value indicative of a temperature of the aerosol-forming substrate; and a controller for controlling the temperature of the aerosol-forming substrate by changing a parameter or configuration of the aerosol-generating device based on a signal from the temperature determining unit.

Description

Dielectric heating aerosol-generating device having a temperature determining unit

The present invention relates to an aerosol-generating device, and specifically to an aerosolgenerating device configured to heat an aerosol-forming substrate by dielectric heating. The present disclosure further relates to a method of dielectrically heating an aerosol-forming substrate by means of an aerosol-generating device, and to an aerosol-generating system comprising an aerosolgenerating device and an aerosol-generating article comprising an aerosol-forming substrate.

Background

Known electrically operated aerosol-generating systems typically heat an aerosol-forming substrate by one or more of: conduction of heat from a heating element to an aerosol-forming substrate, radiation of heat from a heating element to an aerosol-forming substrate or drawing heated air through an aerosol-forming substrate. Most commonly, heating is achieved by passing an electrical current through an electrically resistive heating element, giving rise to Joule heating of the heating element. Inductive heating systems have also been proposed, in which Joule heating occurs as a result of eddy currents induced in a susceptor heating element.

A problem with these heating mechanisms is that they may give rise to non-uniform heating of the aerosol-forming substrate. The portion of the aerosol-forming substrate closest to the heating element is heated more quickly or to a higher temperature than portions of the aerosol-forming substrate more remote from the heating element.

Systems that dielectrically heat an aerosol-forming substrate have been proposed, which advantageously provide uniform heating of the aerosol-forming substrate. However, known dielectric heating systems are less efficient than inductive heating systems and require complex electrical circuitry in order to achieve the necessary voltages and frequencies for dielectric heating of an aerosol-forming substrate.

Moreover, for ensuring an efficient aerosol generation on the one hand and avoiding hazardous over-heating on the other hand, there may be a need of controlling the temperature of the heated substrate itself within well-defined limits.

It would be desirable to provide a system that dielectrically heats an aerosol-forming substrate with greater efficiency, while still being realisable in a compact or handheld system.

Summary of Invention

According to a first aspect, the disclosure provides an aerosol-generating device for dielectrically heating an aerosol-forming substrate. The aerosol-generating device comprises a power source; an oscillation circuit including a resonant feedback circuit and a switching unit powered by the power source forming a self-oscillating circuit; a dielectric heating element fed by the oscillation circuit, the dielectric heating element being a capacitor for the resonant feedback circuit, the dielectric heating element being arranged for heating the aerosol-forming substrate by dipole rotation when subjected to an alternating electric field caused by the dielectric heating element; a temperature determining unit for measuring a value indicative of a temperature of the aerosol-forming substrate; and a controller for controlling the temperature of the aerosol-forming substrate by changing a parameter or configuration of the aerosol-generating device based on a signal from the temperature determining unit.

The signal from the temperature determining unit may be a time-variable signal. In other words, the controlling of the temperature of the aerosol-forming substrate may be done on basis of a time-variable temperature.

The temperature determining unit may comprise at least one of a temperature sensor, a temperature probe, and a temperature marker.

The oscillation circuit may comprise a resonant feedback circuit including the dielectric heating element, so that the oscillation circuit is self-resonating.

The oscillation circuit may comprise an oscillation unit for controlling the switching unit with a defined switching frequency.

The oscillation unit may comprise a DC-to-AC converter, a stripline oscillator, or an oscillation circuit with an amplifier or buffer.

The oscillation circuit may further comprise a delay line DL (sometimes referred to as a delay element), the delay line DL branching out from a path of the resonant oscillating feedback circuit.

A delay-line oscillator is a form of electronic oscillator that uses a delay line, or delay element as its principal timing element. A delay-line oscillator may be set to oscillate by inverting the output of the delay line or delay element and feeding that signal back to the input of the delay line or delay element with appropriate amplification.

The delay element may be realized with a physical delay line (such as an LC network or a transmission line). In some examples, capacitances and inductances may be distributed across the length of the delay element. In some examples, the delay element comprises a cascade of logic gates for creating a gate delay. The timing of an oscillation circuit using a physical delay element may be much more accurate. It is also easier to get such an oscillation circuit to oscillate in the desired mode.

The change of the parameter or configuration of the aerosol-generating device may include enabling or disabling the switching unit by respectively establishing or disabling an electrical connection between the power source and the switching unit.

The change of the parameter or configuration of the aerosol-generating device may include enabling or disabling the switching unit by using a biasing circuit to respectively enable or disable a switching of a transistor of the switching unit by moving the switching unit into an inoperable range of voltage or current.

The change of the parameter or configuration of the aerosol-generating device may include enabling or disabling the switching unit by respectively enabling or disabling the resonant feedback circuit. The change of the parameter or configuration of the aerosol-generating device may include changing a switching frequency of the switching unit.

The change of the parameter or configuration of the aerosol-generating device may include controlling by the controller a level of the DC supply voltage provided by the power source based on a signal from the temperature determining unit.

The aerosol-generating device may further comprise a voltage controlling unit electrically interconnected with the power source, configured to provide the DC supply voltage with a timevariable level.

The voltage controlling unit may include a DC-DC converter, preferably a boost, buck, halfbridge, or full bridge converter, a voltage regulator, a charge pump circuit, or a combination thereof.

The DC supply voltage may be provided as the output voltage of a voltage regulator or of a DC-DC converter.

The change of the parameter or configuration of the aerosol-generating device may be performed so that the oscillation circuit may be enabled when the temperature of the aerosol-forming substrate is below or at a first threshold value, and the oscillation circuit may be disabled when the temperature of the aerosol-forming substrate is above or at a second threshold value.

The change of the parameter or configuration of the aerosol-generating device may be performed by controlling the heating of the aerosol-forming substrate in a pulse width modulation, PWM, operation, wherein a ratio of a heating time duration to a non-heating time duration may be changed based on a signal from the temperature determining unit by respectively enabling and disabling the oscillation circuit.

The signal from the temperature determining unit may be compared to a defined set value, and wherein the change of the parameter or configuration of the aerosol-generating device may be performed in response to a result of the comparison, so that a closed loop temperature control may be performed.

The controller may be operable to control the temperature of the aerosol-forming substrate by first applying a preheating phase to reach a first target temperature at which at least one component of the aerosol-forming substrate vaporizes or at which a maintenance heat level is reached.

In particular, the latter could be above or even below the former, in case some maintenance heat is provided by the dielectric heater, but in any case we would like to get over the vaporization temperature of water.

The controller may be operable to control the temperature of the aerosol-forming substrate to perform, after performing the preheating phase, a puff heating phase where the temperature is maintained at least at a second target temperature. The controller may be operable to provide a first heating power during the preheating phase, the first heating power being higher than a second heating power provided during the puff heating phase.

The controller may be operable to provide to the oscillation circuit, during the preheating phase, at least 70% of a maximum supply voltage of the power source, preferably more than 80% of the maximum supply voltage of the power source.

The controller may be operable to provide to the oscillation circuit, during the puff heating phase, between 40% and 60% of a maximum supply voltage of the power source, preferably around 50% of the maximum supply voltage of the power source.

The temperature determining unit may include a temperature sensor that may be operable to capture a temperature of an element that is separate to the aerosol-forming substrate placed such that it is exposed to the alternating electric field of the dielectric heating element.

The element may be made of at least one material that has a dielectric constant that is similar to the aerosol-forming substrate.

The dielectric heating element may comprise at least two electrodes that are placed on or inside a dielectric carrier film or material, and wherein the temperature determining unit may be operable to capture the temperature of the dielectric carrier film or material.

The temperature determining unit may be arranged on, at, or within a dielectric carrier film or material between two neighboring electrodes of opposite polarity.

Advantageously, interdigitated electrodes with opposite polarity next to each other can be provided, rolled into a tubular form. The temperature sensing could be done there.

The dielectric heating element may comprise at least two electrically conductive electrodes and wherein the temperature determining unit may be operable to capture a temperature of at least one of the electrodes.

The temperature determining unit may comprise a thermistor, a resistance-based temperature detector, a thermocouple, a fiber-optic temperature sensor, or a thermopile.

The temperature determining unit may comprise a non-contact temperature sensor arranged for detecting a heat radiation indicative of the temperature of the aerosol-forming substrate.

The temperature determining device may comprise an infrared temperature sensor, an infrared camera, a pyrometer, a pyroelectric sensor, a time-of-flight sensor, or a combination thereof.

An aerosol-generating article comprising the aerosol-forming substrate may include a plate or surface exposed towards the temperature sensor when the aerosol forming substrate is in operational connection with the dielectric heating element, the plate or surface having an increased thermal radiation emissivity compared to materials used for the aerosol-forming substrate.

The temperature determining unit may comprise a temperature probe arranged for penetrating the aerosol-forming substrate, when the aerosol-forming substrate may be arranged in operational connection with the dielectric heating element. The temperature determining unit may comprise an electric field probe or electric field sensor.

The electric field probe or electric field sensor may comprise a dielectric resonator or antenna for detecting an electric field at the aerosol-forming substrate, and wherein the controller may be operable to derive the temperature of the aerosol-forming substrate from the detected electric field.

The the temperature determining unit may be operable to determine the temperature of the aerosol-forming substrate based on at least one of a heating cavity temperature, a DC supply voltage, a DC supply current, and/or DC supply power.

The controller may comprise a trained artificial intelligence network for deriving the temperature of the aerosol-forming substrate based on measured values, the measured values including at least one of the heating cavity temperature, the DC supply voltage or current, power consumption, an electronic circuit temperature, and a revolving time value.

The trained artificial intelligence network can be an algorithm, a look-up table or the like; a heating session, whether puff based or time based, will have a starting time and an end time, this revolving time information can be used to determine what temperature has been reached, for example together with other time values. Also, every electronic device may have at least one temperature sensor on the electric circuitry, which basically gives some value indicative of the environmental temperature. That value can also be used for the temperature estimation of the substrate.

The temperature determining unit may comprise a current sensor for monitoring changes of a heating power, in particular a DC supply current, and wherein the controller may be operable to derive the temperature of the aerosol-forming substrate from the detected changes in the heating power, in particular the DC supply current.

The temperature determining unit may comprise at least one temperature marker, the temperature marker transitioning from a first physical state into a second physical state when reaching a defined marker temperature.

The temperature determining unit further may comprise a coil configured to magnetize the temperature marker, and the temperature marker may comprise a magnetic susceptor having a Curie temperature defining the marker temperature, wherein a magnetic characteristic of the temperature marker changes when reaching the marker temperature when magnetized by the coil.

The temperature marker may comprise a dielectric marker, the dielectric marker changing a dielectric characteristic when reaching the marker temperature.

The temperature marker may be placed to be exposed to the electric field, and/or may be arranged inside a substrate of the aerosol-forming article, and/or may be an element of a low dielectric carrier film.

For example, it is possible that one or more layers of the carrier film have dielectric marker properties (for example Polyethylene terephthalate (PET)). The dielectric marker may comprise water and the marker temperature may be an evaporation temperature of water.

The aerosol-generating device may comprise a flexible low-dielectric carrier film, wherein at least a part of the oscillation circuit may be formed on the flexible low-dielectric carrier film.

The temperature determining unit may be formed on or within the flexible low-dielectric carrier film.

The temperature sensor of the temperature determining unit may be arranged to at least partly be received within the aerosol-forming substrate.

The temperature sensor of the temperature determining unit may be formed to encompass at least a part of the aerosol-forming substrate.

According to a second aspect, the disclosure provides a method of dielectrically heating an aerosol-forming substrate by means of an aerosol-generating device, the method comprising the following steps: dielectrically heating the aerosol-forming substrate by dipole rotation when subjected to an alternating electric field caused by a dielectric heating element, wherein the dielectric heating element may be comprised in an oscillation circuit of the aerosol-generating device, the dielectric heating element being a capacitor for the resonant feedback circuit, the oscillation circuit including a resonant feedback circuit and a switching unit powered by a power source forming a self-oscillating circuit; measuring a value indicative of a temperature of the aerosol-forming substrate; and controlling the temperature of the aerosol-forming substrate by changing a parameter or configuration of the aerosol-generating device based on the measured value.

The oscillation circuit may comprise a resonant feedback circuit including the dielectric heating element, so that the oscillation circuit may be self-resonating.

A voltage controlling unit electrically interconnected with the power source may be configured to provide the DC supply voltage with a time-variable level.

The voltage control unit may include a DC-DC converter, preferably a boost, buck, halfbridge, or full bridge converter, a voltage regulator, a charge pump circuit, or a combination thereof.

The the signal from the temperature determining unit may be compared to a defined set value, and wherein the change of the parameter or configuration of the aerosol-generating device may be performed in response to a result of the comparison, so that a closed loop temperature control may be performed.

The temperature of the aerosol-forming substrate may be controlled by first applying a preheating phase to reach a first target temperature at which at least one component of the aerosolforming substrate vaporizes or at which a maintenance heat level is reached.

The first target temperature could also be below a temperature at which at least one component of the aerosol-forming substrate vaporizes, in case some maintenance heat is provided by the dielectric heater. In any case, the first target temperature may be over the vaporization temperature of water.

After performing the preheating phase, a puff heating phase may be performed where the temperature is maintained at least at a second target temperature.

A first heating power may be provided during the preheating phase, the first heating power being higher than a second heating power provided during the puff heating phase. During the preheating phase, at least 70% of a maximum supply voltage of the power source, preferably more than 80% of the maximum supply voltage of the power source, may be provided to the oscillation circuit.

During the puff heating phase, between 40% and 60% of a maximum supply voltage of the power source, preferably around 50% of the maximum supply voltage of the power source, may be provided to the oscillation circuit.

The controller may further determine whether a user session has started and applies the preheating phase in response to the start of the user session.

The temperature determining unit may include a temperature sensor that may be operable to capture a temperature of an element that may be separate to the aerosol-forming substrate placed such that it is exposed to the alternating electric field of the dielectric heating element.

An aerosol-generating article comprising the aerosol-forming substrate may include a plate or surface exposed towards the temperature sensor when the aerosol forming substrate may be operational connection with the dielectric heating element, the plate or surface having an increased thermal radiation emissivity compared to the materials used for the aerosol-forming substrate.

The temperature determining unit may comprise an electric field probe or electric field sensor.

The electric field probe or electric field sensor may comprise a temperature probe that can penetrate the aerosol-forming substrate, when the aerosol-forming substrate may be arranged in operational connection with the dielectric heating element. The temperature determining unit may comprise a dielectric resonator or antenna for detecting an electric field at the aerosol-forming substrate, and wherein the controller derives the temperature of the aerosol-forming substrate from the detected electric field.

The temperature determining unit may be operable to determine the temperature of the aerosol-forming substrate based on at least one of a heating cavity temperature, a DC supply voltage, a DC supply current, and/or a DC supply power.

The temperature may comprise a dielectric marker, the dielectric marker changing a dielectric characteristic when reaching the marker temperature.

The dielectric marker may comprise water and the marker temperature may be an evaporation temperature of water.

According to a third aspect, the disclosure provides an aerosol-generating system comprising an aerosol-generating article comprising an aerosol-forming substrate and an aerosol-generating device for dielectrically heating the aerosol-forming substrate, the aerosol-generating device comprising a power source; an oscillation circuit including a resonant feedback circuit and a switching unit powered by the power source forming a self-oscillating circuit; a dielectric heating element fed by the oscillation circuit, the dielectric heating element being a capacitor for the resonant feedback circuit, the dielectric heating element being arranged for heating the aerosol-forming substrate by dipole rotation when subjected to an alternating electric field caused by the dielectric heating element; a temperature determining unit for measuring a value indicative of a temperature of the aerosol-forming substrate; and a controller for controlling the temperature of the aerosolforming substrate by changing a parameter or configuration of the aerosol-generating device based on a signal from the temperature determining unit.

The aerosol-forming substrate may comprise a solid material with an aerosol former.

The dielectric heating element may be formed as a separate insertable and removable part of the aerosol-generating device.

The aerosol-forming substrate may include a plate or surface exposed towards the temperature sensor when the aerosol forming substrate may be operational connection with the dielectric heating element, the plate or surface having an increased thermal radiation emissivity compared to materials used for the aerosol-forming substrate.

The temperature determining unit may comprise a temperature probe that can penetrate the aerosol-forming substrate, when the aerosol-forming substrate may be arranged in operational connection with the dielectric heating element.

The temperature determining unit may be operable to capture a temperature of an element that is separate to the aerosol-forming substrate placed such that it is exposed to the alternating electric field of the dielectric heating element.

The temperature determining unit may be at least partly received within the solid material.

The temperature determining unit may be formed to encompass at least a part of the solid material.

The oscillation circuit may comprise a resonant feedback circuit including the dielectric heating element, so that the oscillation circuit may be self-resonating. The oscillation circuit may comprise an oscillation unit for controlling the switching unit with a defined switching frequency.

The change of the parameter or configuration of the aerosol-generating device may include enabling or disabling the switching unit by respectively enabling or disabling the resonant feedback circuit.

The change of the parameter or configuration of the aerosol-generating device may include changing a switching frequency of the switching unit.

The aerosol-generating system may further comprise a voltage controlling unit electrically interconnected with the power source, configured to provide the DC supply voltage with a timevariable level.

The change of the parameter or configuration of the aerosol-generating device may be performed so that the oscillation circuit is enabled when the temperature of the aerosol-forming substrate is below or at a first threshold value, and the oscillation circuit may be disabled when the temperature of the aerosol-forming substrate is above or at a second threshold value.

The signal from the temperature determining unit may be compared to a defined set value, and wherein the change of the parameter or configuration of the aerosol-generating device may be performed in response to a result of the comparison, so that a closed loop temperature control is performed.

The controller may be operable to control the temperature of the aerosol-forming substrate to perform, after performing the preheating phase, a puff heating phase where the temperature may be maintained at least at a second target temperature.

The controller may be operable to provide a first heating power during the preheating phase, the first heating power being higher than a second heating power provided during the puff heating phase.

The temperature determining unit may include a temperature sensor that may be operable to capture a temperature of an element that may be separate to the aerosol-forming substrate placed such that is exposed to the alternating electric field of the dielectric heating element.

The dielectric heating element may comprise at least two electrodes that are placed on or inside a dielectric carrier, and wherein the temperature determining unit may be operable to capture the temperature of the dielectric carrier film or material.

The temperature determining unit may comprise a non-contact temperature sensor arranged for detecting a heat radiation indicative of the temperature of the aerosol-forming substrate. The temperature determining device may comprise an infrared temperature sensor, an infrared camera, a pyrometer, a pyroelectric sensor, a time-of-flight sensor, or a combination thereof.

The aerosol-generating article or aerosol-forming substrate may include a plate or surface exposed towards the temperature sensor when the aerosol forming substrate is in operational connection with the dielectric heating element, the plate or surface having an increased thermal radiation emissivity compared to materials used for the aerosol-forming substrate.

The temperature determining unit may be operable to determine the temperature of the aerosol-forming substrate based on at least one of a heating cavity temperature, a DC supply voltage, a DC supply current, and/or DC supply power.

The temperature determining unit may further comprise a coil configured to magnetize the temperature marker, and the temperature marker may comprise a magnetic susceptor having a Curie temperature defining the marker temperature, wherein a magnetic characteristic of the temperature marker changes when reaching the marker temperature when magnetized by the coil.

The temperature marker may be placed to be exposed to the electric field, and/or may be arranged inside a substrate of the aerosol-forming article, and/or may be an element of a low dielectric carrier film. The dielectric marker may comprise water and the marker temperature may be an evaporation temperature of water.

The aerosol-generating device may comprise a flexible low-dielectric carrier film and wherein at least a part of the oscillation circuit may be formed on the flexible low-dielectric carrier film.

The temperature determining unit may be formed on or within the low-dielectric carrier film.

A target aerosolization temperature may be in between 80°C to 365°C, preferably 180°C to 320°C, more preferably 180°C to 220°C.

The controller may cause dielectric heating of the aerosol-forming substrate 110 that is located between the two electrodes with an average dielectric heating power density in a range between 1W/cm³ to 25W/cm³, preferably between 1.5W/cm³ and 15W/cm³ per volume of substrate material during a time period of less than 15 minutes. In particular, during a heat-up phase, the average dielectric heating power density may be controlled or set to be in a range between 7W/cm³ to 25W/cm³, preferably between 8W/cm³ to 20W/cm³. During a target heating phase (also called maintenance heating phase) during consumption, the average dielectric heating power density is in a range between 1W/cm³ to 7W/cm³, preferably between 1W/cm³ to 5W/cm³.

In an example, the feedback loop may be suspended between a power supply and ground of the oscillation circuit, meaning that there is no direct connection between the feedback loop and the supply voltage or ground - e.g., there may be at least one electrical component (for examples, a resistor or capacitor) creating a non-negligible potential difference between the feedback loop and the power supply and ground in the oscillation circuit. This may reduce noise and ground influences for more predictable operation in the feedback loop.

As used herein, the term “aerosol-generating device” relates to a device that interacts with an article comprising an aerosol-forming substrate to generate an aerosol.

As used herein, the term “aerosol-forming substrate” relates to a substrate capable of releasing volatile compounds that can form an aerosol. Such volatile compounds can be released by heating the aerosol-forming substrate.

As used herein, the term “puff” means the action of a user drawing an aerosol into their body through their mouth or nose.

As used herein, the term “relative permittivity” (also known as dielectric constant) relates to the permittivity of a material that forms the aerosol-forming substrate expressed as a ratio with the permittivity of vacuum. Mathematically, relative permittivity is expressed as the following: er = e/eO. The parameters in this equation are defined as follows: e is the permittivity of a material that forms the substrate; eO is the permittivity of vacuum; and er is the relative permittivity of a material that forms the substrate. In particular, the term “relative permittivity” may also be referred to as the real part of the complex, frequency-dependent relative permittivity, measured at a temperature of 20°C, in an alternating electric field with at a very low frequency (VLF) of 1 Kilohertz or less, as defined in the international standard IEC 62631-2-1 :2018. It will be appreciated that the frequency value of 1 Kilohertz is included here solely as a general reference and other definitions may use different frequencies.

The invention is defined in the claims. However, below there is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

Example Ex1. An aerosol-generating device for dielectrically heating an aerosol-forming substrate, the aerosol-generating device comprising: a power source; an oscillation circuit powered by the power source; a dielectric heating element fed by the oscillation circuit, the dielectric heating element being arranged for heating the aerosol-forming substrate by dipole rotation when subjected to an alternating electric field caused by the dielectric heating element; a temperature determining unit for measuring a value indicative of a temperature of the aerosol-forming substrate; and a controller for controlling the temperature of the aerosol-forming substrate by changing a parameter or configuration of the aerosol-generating device based on a signal from the temperature determining unit.

Example Ex2. The aerosol-generating device according to Ex1 , wherein the oscillation circuit comprises a resonant feedback circuit including the dielectric heating element, so that the oscillation circuit is self-resonating.

Example Ex3. The aerosol-generating device according to Ex1 , wherein the oscillation circuit comprises an oscillation unit for controlling the switching unit with a defined switching frequency.

Example Ex4. The aerosol-generating device according to Ex3, wherein the oscillation unit comprises a DC-to-AC converter, a stripline oscillator, or an oscillation circuit with an amplifier or buffer.

Example Ex5. The aerosol-generating device according to any of the preceding examples, wherein the change of the parameter or configuration of the aerosol-generating device includes enabling or disabling the switching unit by respectively establishing or disabling an electrical connection between the power source and the switching unit.

Example Ex6. The aerosol-generating device according to any of the preceding examples, wherein the change of the parameter or configuration of the aerosol-generating device includes enabling or disabling the switching unit by using a biasing circuit to respectively enable or disable a switching of a transistor of the switching unit by moving the switching unit into an inoperable range of voltage or current.

Example Ex7. The aerosol-generating device according to any of the preceding examples, wherein the change of the parameter or configuration of the aerosol-generating device includes enabling or disabling the switching unit by respectively enabling or disabling the resonant feedback circuit.

Example Ex8. The aerosol-generating device according to any of the preceding examples, wherein the change of the parameter or configuration of the aerosol-generating device includes changing a switching frequency of the switching unit.

Example Ex9. The aerosol-generating device according to any of the preceding examples, wherein the change of the parameter or configuration of the aerosol-generating device includes controlling by the controller a level of the DC supply voltage provided by the power source based on a signal from the temperature determining unit.

Example Ex10. The aerosol-generating device according to Ex9, further comprising a voltage controlling unit electrically interconnected with the power source, configured to provide the DC supply voltage with a time-variable level.

Example Ex11. The aerosol-generating device according to Ex10, wherein the voltage controlling unit includes a DC-DC converter, preferably a boost, buck, half-bridge, or full bridge converter, a voltage regulator, a charge pump circuit, or a combination thereof.

Example Ex12. The aerosol-generating device according to any of the Ex9 to Ex11 , wherein the DC supply voltage is provided as the output voltage of a voltage regulator or of a DC-DC converter.

Example Ex13. The aerosol-generating device according to any of the preceding examples, wherein the change of the parameter or configuration of the aerosol-generating device is performed so that the oscillation circuit is enabled when the temperature of the aerosol-forming substrate is below or at a first threshold value, and the oscillation circuit is disabled when the temperature of the aerosol-forming substrate is above or at a second threshold value.

Example Ex14. The aerosol-generating device according to any of the preceding examples, wherein the change of the parameter or configuration of the aerosol-generating device is performed by controlling the heating of the aerosol-forming substrate in a pulse width modulation, PWM, operation, wherein a ratio of a heating time duration to a non-heating time duration is changed based on a signal from the temperature determining unit by respectively enabling and disabling the oscillation circuit.

Example Ex15. The aerosol-generating device according to any of the preceding examples, wherein the signal from the temperature determining unit is compared to a defined set value, and wherein the change of the parameter or configuration of the aerosol-generating device is performed in response to a result of the comparison, so that a closed loop temperature control is performed.

Example Ex16. The aerosol-generating device according to any of the preceding examples, wherein the controller is operable to control the temperature of the aerosol-forming substrate by first applying a preheating phase to reach a first target temperature at which at least one component of the aerosol-forming substrate vaporizes or at which a maintenance heat level is reached.

Example Ex17. The aerosol-generating device according to Ex16, wherein the controller is operable to control the temperature of the aerosol-forming substrate to perform, after performing the preheating phase, a puff heating phase where the temperature is maintained at least at a second target temperature.

Example Ex18. The aerosol-generating device according to any of Ex16 or Ex17, wherein the controller is operable to provide a first heating power during the preheating phase, the first heating power being higher than a second heating power provided during the puff heating phase.

Example Ex19. The aerosol-generating device according to any of Ex16 to Ex18, wherein the controller is operable to provide to the oscillation circuit, during the preheating phase, at least 70% of a maximum supply voltage of the power source, preferably more than 80% of the maximum supply voltage of the power source.

Example Ex20. The aerosol-generating device according to any of Ex17 to Ex19, wherein the controller is operable to provide to the oscillation circuit, during the puff heating phase, between 40% and 60% of a maximum supply voltage of the power source, preferably around 50% of the maximum supply voltage of the power source.

Example Ex21. The aerosol-generating device according to any of the preceding examples, wherein the temperature determining unit includes a temperature sensor that is operable to capture a temperature of an element that is separate to the aerosol-forming substrate placed such that is exposed to the alternating electric field of the dielectric heating element.

Example Ex22. The aerosol-generating device according to Ex21 , wherein the element is made of at least one material that has a dielectric constant that is similar to the aerosolforming substrate.

Example Ex23. The aerosol-generating device according to any of the preceding examples, wherein the dielectric heating element comprises at least two electrodes that are placed on or inside a dielectric carrier film or material, and wherein the temperature determining unit is operable to capture the temperature of the dielectric carrier film or material.

Example Ex24. The aerosol-generating device according to any of the preceding examples, wherein the temperature determining unit is arranged on, at, or within a dielectric carrier film or material between two neighboring electrodes of opposite polarity.

Example Ex25. The aerosol-generating device according to any of the preceding examples, wherein the dielectric heating element comprises at least two electrically conductive electrodes and wherein the temperature determining unit is operable to capture a temperature of at least one of the electrodes. Example Ex26. The aerosol-generating device according to any of the preceding examples, wherein the temperature determining unit comprises a thermistor, a resistance-based temperature detector, a thermocouple, a fiber-optic temperature sensor, or a thermopile.

Example Ex27. The aerosol-generating device according to any of the preceding examples, wherein the temperature determining unit comprises a non-contact temperature sensor arranged for detecting a heat radiation indicative of the temperature of the aerosol-forming substrate.

Example Ex28. The aerosol-generating device according to Ex27, wherein the temperature determining device comprises an infrared temperature sensor, an infrared camera, a pyrometer, a pyroelectric sensor, a time-of-flight sensor, or a combination thereof.

Example Ex29. The aerosol-generating device according to any of Ex21 to Ex28, wherein an aerosol-generating article comprising the aerosol-forming substrate includes a plate or surface exposed towards the temperature sensor when the aerosol forming substrate is operational connection with the dielectric heating element, the plate or surface having an increased thermal radiation emissivity compared to materials used for the aerosol-forming substrate.

Example Ex30. The aerosol-generating device according to any of the preceding examples, wherein the temperature determining unit comprises a temperature probe arranged for penetrating the aerosol-forming substrate, when the aerosol-forming substrate is arranged in operational connection with the dielectric heating element.

Example Ex31. The aerosol-generating device according to any of the preceding examples, wherein the temperature determining unit comprises an electric field probe or electric field sensor.

Example Ex32. The aerosol-generating device according to Ex31 , wherein the electric field probe or electric field sensor comprises a dielectric resonator or antenna for detecting an electric field at the aerosol-forming substrate, and wherein the controller is operable to derive the temperature of the aerosol-forming substrate from the detected electric field.

Example Ex33. The aerosol-generating device according to any of the preceding examples, wherein the temperature determining unit is operable to determine the temperature of the aerosol-forming substrate based on at least one of a heating cavity temperature, a DC supply voltage, a DC supply current, and/or DC supply power.

Example Ex34. The aerosol-generating device according to Ex33, wherein the controller comprises a trained artificial intelligence network for deriving the temperature of the aerosol-forming substrate based on measured values, the measured values including at least one of the heating cavity temperature, the DC supply voltage or current, power consumption, an electronic circuit temperature, and a revolving time value.

Example Ex35. The aerosol-generating device according to any of the preceding examples, wherein the temperature determining unit comprises a current sensor for monitoring changes of a heating power, in particular a DC supply current, and wherein the controller is operable to derive the temperature of the aerosol-forming substrate from the detected changes in the heating power, in particular the DC supply current.

Example Ex36. The aerosol-generating device according to any of the preceding examples, wherein the temperature determining unit comprises at least one temperature marker, the temperature marker transitioning from a first physical state into a second physical state when reaching a defined marker temperature.

Example Ex37. The aerosol-generating device according to Ex36, wherein the temperature determining unit further comprises a coil configured to magnetize the temperature marker, and the temperature marker comprises a magnetic susceptor having a Curie temperature defining the marker temperature, wherein a magnetic characteristic of the temperature marker changes when reaching the marker temperature when magnetized by the coil.

Example Ex38. The aerosol-generating device according to Ex36, wherein the temperature marker comprises a dielectric marker, the dielectric marker changing a dielectric characteristic when reaching the marker temperature.

Example Ex39. The aerosol-generating device according to Ex38, wherein the temperature marker is placed to be exposed to the electric field, and/or is arranged inside a substrate of the aerosol-forming article, and/or is an element of a low dielectric carrier film.

Example Ex40. The aerosol-generating device according to Ex38 or Ex39, wherein the dielectric marker comprises water and the marker temperature is an evaporation temperature of water.

Example Ex41. The aerosol-generating device according to any of the preceding examples, wherein the aerosol-generating device comprises a flexible low-dielectric carrier film and wherein at least a part of the oscillation circuit is formed on the flexible low-dielectric carrier film.

Example Ex42. The aerosol-generating device according to Ex41 , wherein the temperature determining unit is formed on or within the flexible low-dielectric carrier film.

Example Ex43. The aerosol-generating device according to any of the preceding examples, wherein the temperature sensor of the temperature determining unit is arranged to at least partly be received within the aerosol-forming substrate.

Example Ex44. The aerosol-generating device according to any of the preceding examples, wherein the temperature sensor of the temperature determining unit is formed to encompass at least a part of the aerosol-forming substrate.

Example Ex45. A method of dielectrically heating an aerosol-forming substrate by means of an aerosol-generating device, the method comprising the following steps: dielectrically heating the aerosol-forming substrate by dipole rotation when subjected to an alternating electric field caused by a dielectric heating element, wherein the dielectric heating element is comprised in an oscillation circuit of the aerosol-generating device, the oscillation circuit being fed by a power source; measuring a value indicative of a temperature of the aerosol-forming substrate; and controlling the temperature of the aerosol-forming substrate by changing a parameter or configuration of the aerosol-generating device based on the measured value.

Example Ex46. The method according to Ex45, wherein the oscillation circuit comprises a resonant feedback circuit including the dielectric heating element, so that the oscillation circuit is self-resonating.

Example Ex47. The method according to Ex45, wherein the oscillation circuit comprises an oscillation unit for controlling the switching unit with a defined switching frequency.

Example Ex48. The method according to Ex47, wherein the oscillation unit comprises a DC-to-AC converter, a stripline oscillator, or an oscillation circuit with an amplifier or buffer.

Example Ex49. The method according to any of Ex45 to Ex48, wherein the change of the parameter or configuration of the aerosol-generating device includes enabling or disabling the switching unit by respectively establishing or disabling an electrical connection between the power source and the switching unit.

Example Ex50. The method according to any of Ex45 to Ex49, wherein the change of the parameter or configuration of the aerosol-generating device includes enabling or disabling the switching unit by using a biasing circuit to respectively enable or disable a switching of a transistor of the switching unit by moving the switching unit into an inoperable range of voltage or current.

Example Ex51. The method according to any of Ex45 to Ex50, wherein the change of the parameter or configuration of the aerosol-generating device includes enabling or disabling the switching unit by respectively enabling or disabling the resonant feedback circuit.

Example Ex52. The method according to any of Ex45 to Ex51 , wherein the change of the parameter or configuration of the aerosol-generating device includes changing a switching frequency of the switching unit.

Example Ex53. The method according to any of the Ex45 to Ex52, wherein the change of the parameter or configuration of the aerosol-generating device includes controlling by the controller a level of the DC supply voltage provided by the power source based on a signal from the temperature determining unit.

Example Ex54. The method according to Ex53, wherein a voltage controlling unit electrically interconnected with the power source is configured to provide the DC supply voltage with a time-variable level.

Example Ex55. The method according to Ex54, wherein the voltage control unit includes a DC-DC converter, preferably a boost, buck, half-bridge, or full bridge converter, a voltage regulator, a charge pump circuit, or a combination thereof.

Example Ex56. The method according to any of Ex53 to Ex55, wherein the DC supply voltage is provided as the output voltage of a voltage regulator or of a DC-DC converter.

Example Ex57. The method according to any of Ex49 to Ex56, wherein the change of the parameter or configuration of the aerosol-generating device is performed so that the oscillation circuit is enabled when the temperature of the aerosol-forming substrate is below or at a first threshold value, and the oscillation circuit is disabled when the temperature of the aerosol-forming substrate is above or at a second threshold value.

Example Ex58. The method according to any of Ex45 to Ex57, wherein the change of the parameter or configuration of the aerosol-generating device is performed by controlling the heating of the aerosol-forming substrate in a pulse width modulation, PWM, operation, wherein a ratio of a heating time duration to a non-heating time duration is changed based on a signal from the temperature determining unit by respectively enabling and disabling the oscillation circuit.

Example Ex59. The method according to any of Ex45 to Ex58, wherein the signal from the temperature determining unit is compared to a defined set value, and wherein the change of the parameter or configuration of the aerosol-generating device is performed in response to a result of the comparison, so that a closed loop temperature control is performed.

Example Ex60. The method according to any of the Ex45 to Ex59, wherein the temperature of the aerosol-forming substrate is controlled by first applying a preheating phase to reach a first target temperature at which at least one component of the aerosol-forming substrate vaporizes or at which a maintenance heat level is reached.

Example Ex61. The method according to Ex60, wherein, after performing the preheating phase, a puff heating phase is performed where the temperature is maintained at least at a second target temperature.

Example Ex62. The method according to any of Ex60 or Ex61 , wherein a first heating power is provided during the preheating phase, the first heating power being higher than a second heating power provided during the puff heating phase.

Example Ex63. The method according to any of Ex60 to Ex62, wherein, during the preheating phase, at least 70% of a maximum supply voltage of the power source, preferably more than 80% of the maximum supply voltage of the power source, is provided to the oscillation circuit.

Example Ex64. The method according to any of Ex61 to Ex63, wherein, during the puff heating phase, between 40% and 60% of a maximum supply voltage of the power source, preferably around 50% of the maximum supply voltage of the power source, is provided to the oscillation circuit.

Example Ex65. The method according to any of Ex45 to Ex64, wherein the controller further determines whether a user session has started and applies the preheating phase in response to the start of the user session.

Example Ex66. The method according to any of the Ex45 to Ex65, wherein the temperature determining unit includes a temperature sensor that is operable to capture a temperature of an element that is separate to the aerosol-forming substrate placed such that is exposed to the alternating electric field of the dielectric heating element.

Example Ex67. The method according to Ex66, wherein the element is made of at least one material that has a dielectric constant that is similar to the aerosol-forming substrate. Example Ex68. The method according to any of the Ex45 to Ex67, wherein the dielectric heating element comprises at least two electrodes that are placed on or inside a dielectric carrier film or material, and wherein the temperature determining unit is operable to capture the temperature of the dielectric carrier film or material.

Example Ex69. The method according to any of Ex45 to Ex68, wherein the temperature determining unit is arranged on, at, or within a dielectric carrier film or material between two neighboring electrodes of opposite polarity.

Example Ex70. The method according to any of Ex45 to Ex69, wherein the dielectric heating element comprises at least two electrically conductive electrodes and wherein the temperature determining unit is operable to capture a temperature of at least one of the electrodes.

Example Ex71. The method according to any of Ex45 to Ex70, wherein the temperature determining unit comprises a thermistor, a resistance-based temperature detector, a thermocouple, a fiber-optic temperature sensor, or a thermopile.

Example Ex72. The method according to any of Ex45 to Ex71 , wherein the temperature determining unit comprises a non-contact temperature sensor arranged for detecting a heat radiation indicative of the temperature of the aerosol-forming substrate.

Example Ex73. The method according to Ex72, wherein the temperature determining device comprises an infrared temperature sensor, an infrared camera, a pyrometer, a pyroelectric sensor, a time-of-f light sensor, or a combination thereof.

Example Ex74. The method according to any of the Ex66 to Ex73, wherein an aerosolgenerating article comprising the aerosol-forming substrate includes a plate or surface exposed towards the temperature sensor when the aerosol forming substrate is operational connection with the dielectric heating element, the plate or surface having an increased thermal radiation emissivity compared to the materials used for the aerosol-forming substrate.

Example Ex75. The method according to any of Ex45 to Ex74, wherein the temperature determining unit comprises an electric field probe or electric field sensor.

Example Ex76. The method according to Ex75, wherein the electric field probe or electric field sensor comprises a temperature probe that can penetrate the aerosol-forming substrate, when the aerosol-forming substrate is arranged in operational connection with the dielectric heating element.

Example Ex77. The method according to any of Ex45 to Ex76, wherein the temperature determining unit comprises a dielectric resonator or antenna for detecting an electric field at the aerosol-forming substrate, and wherein the controller derives the temperature of the aerosol-forming substrate from the detected electric field.

Example Ex78. The method according to any of Ex45 to Ex77, wherein the temperature determining unit is operable to determine the temperature of the aerosol-forming substrate based on at least one of a heating cavity temperature, a DC supply voltage, a DC supply current, and/or a DC supply power.

Example Ex79. The method according to Ex78, wherein the controller comprises a trained artificial intelligence network for deriving the temperature of the aerosol-forming substrate based on measured values, the measured values including at least one of the heating cavity temperature, the DC supply voltage or current, power consumption, an electronic circuit temperature, and a revolving time value.

Example Ex80. The method according to any of the Ex45 to Ex72, wherein the temperature determining unit comprises a current sensor for monitoring changes of a heating power, in particular a DC supply current, and wherein the controller is operable to derive the temperature of the aerosol-forming substrate from the detected changes in the heating power, in particular the DC supply current.

Example Ex81. The method according to any of Ex45 to Ex80, wherein the temperature determining unit comprises at least one temperature marker, the temperature marker transitioning from a first physical state into a second physical state when reaching a defined marker temperature.

Example Ex82. The method according to Ex81 , wherein the temperature determining unit further comprises a coil configured to magnetize the temperature marker, and the temperature marker comprises a magnetic susceptor having a Curie temperature defining the marker temperature, wherein a magnetic characteristic of the temperature marker changes when reaching the marker temperature when magnetized by the coil.

Example Ex83. The method according to Ex81 , wherein the temperature comprises a dielectric marker, the dielectric marker changing a dielectric characteristic when reaching the marker temperature.

Example Ex84. The method according to Ex83, wherein the temperature marker is placed to be exposed to the electric field, and/or is arranged inside a substrate of the aerosol-forming article, and/or is an element of a low dielectric carrier film.

Example Ex84. The method according to Ex83 or Ex84, wherein the dielectric marker comprises water and the marker temperature is an evaporation temperature of water.

Example Ex85. An aerosol-generating system comprising: an aerosol-generating article comprising an aerosol-forming substrate and an aerosol-generating device for dielectrically heating the aerosol-forming substrate, the aerosol-generating device comprising: a power source; an oscillation circuit powered by the power source; a dielectric heating element fed by the oscillation circuit, the dielectric heating element arranged for heating the aerosol-forming substrate by dipole rotation when subjected to an alternating electric field caused by the dielectric heating element; a temperature determining unit for measuring a value indicative of a temperature of the aerosolforming substrate; and a controller for controlling the temperature of the aerosol-forming substrate by changing a parameter or configuration of the aerosol-generating device based on a signal from the temperature determining unit.

Example Ex86. The aerosol-generating system according to Ex85, wherein the aerosol-forming substrate comprises a solid material with an aerosol former.

Example Ex87. The aerosol-generating system according to any of Ex85 or Ex86, wherein the dielectric heating element is formed as a separate insertable and removable part of the aerosol-generating device.

Example Ex88. The aerosol-generating system according to any of Ex85 to Ex87, wherein the temperature determining unit comprises a non-contact temperature sensor arranged for detecting a heat radiation indicative of the temperature of the aerosol-forming substrate.

Example Ex89. The aerosol-generating system according to Ex88, wherein the temperature determining device comprises an infrared temperature sensor, an infrared camera, a pyrometer, a pyroelectric sensor, a time-of-flight sensor, or a combination thereof.

Example Ex90. The aerosol-generating system according to any of Ex85 to Ex89, wherein the aerosol-forming substrate includes a plate or surface exposed towards the temperature sensor when the aerosol forming substrate is operational connection with the dielectric heating element, the plate or surface having an increased thermal radiation emissivity compared to materials used for the aerosol-forming substrate.

Example Ex91. The aerosol-generating system according to any of Ex85 to Ex90, wherein the temperature determining unit comprises a temperature probe that can penetrate the aerosol-forming substrate, when the aerosol-forming substrate is arranged in operational connection with the dielectric heating element.

Example Ex92. The aerosol-generating system according to any of Ex85 to Ex91 , wherein the temperature determining unit is operable to capture a temperature of an element that is separate to the aerosol-forming substrate placed such that is exposed to the alternating electric field of the dielectric heating element.

Example Ex93. The aerosol-generating system according to Ex92, wherein the element is made of at least one material that has a dielectric constant that is similar to the aerosolforming substrate.

Example Ex94. The aerosol-generating system according to any of Ex85 to Ex93, wherein the dielectric heating element comprises at least two electrodes that are placed on or inside a dielectric carrier film or material, and wherein the temperature determining unit is operable to capture the temperature of the dielectric carrier film or material.

Example Ex95. The aerosol-generating system according to any of Ex85 to Ex94, wherein the temperature determining unit is arranged on, at, or within a dielectric carrier film or material between two neighboring electrodes of opposite polarity. Example Ex96. The aerosol-generating system according to any of the Ex85 to Ex95, wherein the dielectric heating element comprises at least two electrically conductive electrodes and wherein the temperature determining unit is operable to capture a temperature of at least one of the electrodes.

Example Ex97. The aerosol-generating system according to any of Ex85 to Ex95, wherein the temperature determining unit comprises a thermistor, a resistance-based temperature detector, a thermocouple, a fiber-optic temperature sensor, or a thermopile.

Example Ex98. The aerosol-generating system according to any of Ex86 to Ex97, wherein the temperature determining unit is at least partly received within the solid material.

Example Ex99. The aerosol-generating system according to any of Ex86 to Ex98, wherein the temperature determining unit is formed to encompass at least a part of the solid material.

Example Ex100. The aerosol-generating system according to any of Ex85 to Ex99, wherein the oscillation circuit comprises a resonant feedback circuit including the dielectric heating element, so that the oscillation circuit is self-resonating.

Example Ex101. The aerosol-generating system according to any of Ex85 to Ex99, wherein the oscillation circuit comprises an oscillation unit for controlling the switching unit with a defined switching frequency.

Example Ex102. The aerosol-generating system according to Ex101 , wherein the oscillation unit comprises a DC-to-AC converter, a stripline oscillator, or an oscillation circuit with an amplifier or buffer.

Example Ex103. The aerosol-generating system according to any of Ex85 to Ex102, wherein the change of the parameter or configuration of the aerosol-generating device includes enabling or disabling the switching unit by respectively establishing or disabling an electrical connection between the power source and the switching unit.

Example Ex104. The aerosol-generating system according to any of Ex85 to Ex103, wherein the change of the parameter or configuration of the aerosol-generating device includes enabling or disabling the switching unit by using a biasing circuit to respectively enable or disable a switching of a transistor of the switching unit by moving the switching unit into an inoperable range of voltage or current.

Example Ex105. The aerosol-generating system according to any of the Ex85 to Ex104, wherein the change of the parameter or configuration of the aerosol-generating device includes enabling or disabling the switching unit by respectively enabling or disabling the resonant feedback circuit.

Example Ex106. The aerosol-generating system according to any of Ex85 to Ex105, wherein the change of the parameter or configuration of the aerosol-generating device includes changing a switching frequency of the switching unit. Example Ex107. The aerosol-generating system according to any of Ex85 to Ex106, wherein the change of the parameter or configuration of the aerosol-generating device includes controlling by the controller a level of the DC supply voltage provided by the power source based on a signal from the temperature determining unit.

Example Ex108. The aerosol-generating system according to Ex107, further comprising a voltage controlling unit electrically interconnected with the power source, configured to provide the DC supply voltage with a time-variable level.

Example Ex109. The aerosol-generating system according to any of Ex107 or Ex108, wherein the voltage control unit includes a DC-DC converter, preferably a boost, buck, half-bridge, or full bridge converter, a voltage regulator, a charge pump circuit, or a combination thereof.

Example Ex110. The aerosol-generating system according to any of Ex107 to Ex109, wherein the DC supply voltage is provided as the output voltage of a voltage regulator or of a DC- DC converter.

Example Ex111. The aerosol-generating system according to any of Ex85 to Ex110, wherein the change of the parameter or configuration of the aerosol-generating device is performed so that the oscillation circuit is enabled when the temperature of the aerosol-forming substrate is below or at a first threshold value, and the oscillation circuit is disabled when the temperature of the aerosol-forming substrate is above or at a second threshold value.

Example Ex112. The aerosol-generating system according to any of Ex85 to Ex111 , wherein the change of the parameter or configuration of the aerosol-generating device is performed by controlling the heating of the aerosol-forming substrate in a pulse width modulation, PWM, operation, wherein a ratio of a heating time duration to a non-heating time duration is changed based on a signal from the temperature determining unit by respectively enabling and disabling the oscillation circuit.

Example Ex113. The aerosol-generating system according to any of Ex85 to Ex112, wherein the signal from the temperature determining unit is compared to a defined set value, and wherein the change of the parameter or configuration of the aerosol-generating device is performed in response to a result of the comparison, so that a closed loop temperature control is performed.

Example Ex114. The aerosol-generating system according to any of Ex85 to Ex113, wherein the controller is operable to control the temperature of the aerosol-forming substrate by first applying a preheating phase to reach a first target temperature at which at least one component of the aerosol-forming substrate vaporizes or at which a maintenance heat level is reached.

Example Ex115. The aerosol-generating system according to Ex114, wherein the controller is operable to control the temperature of the aerosol-forming substrate to perform, after performing the preheating phase, a puff heating phase where the temperature is maintained at least at a second target temperature. Example Ex116. The aerosol-generating system according to any of Ex114 or Ex115, wherein the controller is operable to provide a first heating power during the preheating phase, the first heating power being higher than a second heating power provided during the puff heating phase.

Example Ex117. The aerosol-generating system according to any of Ex114 to Ex116, wherein the controller is operable to provide to the oscillation circuit, during the preheating phase, at least 70% of a maximum supply voltage of the power source, preferably more than 80% of the maximum supply voltage of the power source.

Example Ex118. The aerosol-generating system according to any of Ex115 to Ex117, wherein the controller is operable to provide to the oscillation circuit, during the puff heating phase, between 40% and 60% of a maximum supply voltage of the power source, preferably around 50% of the maximum supply voltage of the power source.

Example Ex119. The aerosol-generating system according to any of Ex85 to Ex118, wherein the temperature determining unit includes a temperature sensor that is operable to capture a temperature of an element that is separate to the aerosol-forming substrate placed such that is exposed to the alternating electric field of the dielectric heating element.

Example Ex120. The aerosol-generating system according to Ex119, wherein the element is made of at least one material that has a dielectric constant that is similar to the aerosolforming substrate.

Example Ex121. The aerosol-generating system according to any of Ex85 to Ex120, wherein the dielectric heating element comprises at least two electrodes that are placed on or inside a dielectric carrier, and wherein the temperature determining unit is operable to capture the temperature of the dielectric carrier film or material.

Example Ex122. The aerosol-generating system according to any of the Ex85 to Ex121 , wherein the dielectric heating element comprises at least two electrically conductive electrodes and wherein the temperature determining unit is operable to capture a temperature of at least one of the electrodes.

Example Ex123. The aerosol-generating system according to any of Ex85 to Ex122, wherein the temperature determining unit comprises a thermistor, a resistance-based temperature detector, a thermocouple, a fiber-optic temperature sensor, or a thermopile.

Example Ex124. The aerosol-generating system according to any of Ex85 to Ex123, wherein the temperature determining unit comprises a non-contact temperature sensor arranged for detecting a heat radiation indicative of the temperature of the aerosol-forming substrate.

Example Ex125. The aerosol-generating system according to Ex124, wherein the temperature determining device comprises an infrared temperature sensor, an infrared camera, a pyrometer, a pyroelectric sensor, a time-of-flight sensor, or a combination thereof.

Example Ex126. The aerosol-generating system according to any of Ex119 to Ex125, wherein the aerosol-generating article or aerosol-forming substrate includes a plate or surface exposed towards the temperature sensor when the aerosol forming substrate is operational connection with the dielectric heating element, the plate or surface having an increased thermal radiation emissivity compared to materials used for the aerosol-forming substrate.

Example Ex127. The aerosol-generating system according to any of Ex85 to Ex126, wherein the temperature determining unit comprises a temperature probe that can penetrate the aerosol-forming substrate, when the aerosol-forming substrate is arranged in operational connection with the dielectric heating element.

Example Ex128. The aerosol-generating system according to any of Ex85 to Ex127, wherein the temperature determining unit comprises an electric field probe or electric field sensor.

Example Ex129. The aerosol-generating system according to Ex128, wherein the electric field probe or electric field sensor comprises a dielectric resonator or antenna for detecting an electric field at the aerosol-forming substrate, and wherein the controller is operable to derive the temperature of the aerosol-forming substrate from the detected electric field.

Example Ex130. The aerosol-generating system according to any of Ex85 to Ex129, wherein the temperature determining unit is operable to determine the temperature of the aerosolforming substrate based on at least one of a heating cavity temperature, a DC supply voltage, a DC supply current, and/or DC supply power.

Example Ex131. The aerosol-generating system according to Ex130, wherein the controller comprises a trained artificial intelligence network for deriving the temperature of the aerosol-forming substrate based on measured values, the measured values including at least one of the heating cavity temperature, the DC supply voltage or current, power consumption, an electronic circuit temperature, and a revolving time value.

Example Ex132. The aerosol-generating system according to any of Ex85 to Ex131 , wherein the temperature determining unit comprises a current sensor for monitoring changes of a heating power, in particular a DC supply current, and wherein the controller is operable to derive the temperature of the aerosol-forming substrate from the detected changes in the heating power, in particular the DC supply current.

Example Ex133. The aerosol-generating system according to any of the Ex85 to Ex132, wherein the temperature determining unit comprises at least one temperature marker, the temperature marker transitioning from a first physical state into a second physical state when reaching a defined marker temperature.

Example Ex134. The aerosol-generating system according to Ex133, wherein the temperature determining unit further comprises a coil configured to magnetize the temperature marker, and the temperature marker comprises a magnetic susceptor having a Curie temperature defining the marker temperature, wherein a magnetic characteristic of the temperature marker changes when reaching the marker temperature when magnetized by the coil. Example Ex135. The aerosol-generating system according to Ex134, wherein the temperature comprises a dielectric marker, the dielectric marker changing a dielectric characteristic when reaching the marker temperature.

Example Ex136. The aerosol-generating system according to Ex135, wherein the temperature marker is placed to be exposed to the electric field, and/or is arranged inside a substrate of the aerosol-forming article, and/or is an element of a low dielectric carrier film.

Example Ex137. The aerosol-generating system according to Ex135 or Ex136, wherein the dielectric marker comprises water and the marker temperature is an evaporation temperature of water.

Example Ex138. The aerosol-generating system according to any of Ex85 to Ex137, wherein the aerosol-generating device comprises a flexible low-dielectric carrier film and wherein at least a part of the oscillation circuit is formed on the flexible low-dielectric carrier film.

Example Ex139. The aerosol-generating system according to Ex138, wherein the temperature determining unit is formed on or within the low-dielectric carrier film.

Example Ex140. The aerosol-generating system according to any of Ex119 to Ex139, wherein the temperature sensor of the temperature determining unit is arranged to at least partly be received within the aerosol-forming substrate.

Example Ex141. The aerosol-generating system according to any of Ex119 to Ex140, wherein the temperature sensor of the temperature determining unit is formed to encompass at least a part of the aerosol-forming substrate.

Example Ex142. The aerosol-generating device according to Ex1 , wherein the temperature determining unit comprises at least one of a temperature sensor, a temperature probe, and a temperature marker.

Example Ex143. An aerosol-generating device for dielectrically heating an aerosolforming substrate, the aerosol-generating device comprising: a power source; an oscillation circuit including a resonant feedback circuit and a switching unit powered by the power source forming a self-oscillating circuit; a dielectric heating element fed by the oscillation circuit, the dielectric heating element being a capacitor for the resonant feedback circuit, the dielectric heating element being arranged for heating the aerosol-forming substrate by dipole rotation when subjected to an alternating electric field caused by the dielectric heating element; a temperature determining unit for measuring a value indicative of a temperature of the aerosol-forming substrate; and a controller for controlling the temperature of the aerosol-forming substrate by changing a parameter or configuration of the aerosol-generating device based on a signal from the temperature determining unit. Example Ex144. The aerosol-generating device according to Ex143, wherein the device is adapted according to any one of the Examples Ex2 to Ex44.

Example Ex145. A method of dielectrically heating an aerosol-forming substrate by means of an aerosol-generating device, the method comprising the following steps: dielectrically heating the aerosol-forming substrate by dipole rotation when subjected to an alternating electric field caused by a dielectric heating element, wherein the dielectric heating element is comprised in an oscillation circuit of the aerosol-generating device, the dielectric heating element being a capacitor for the resonant feedback circuit, the oscillation circuit including a resonant feedback circuit and a switching unit powered by a power source forming a self-oscillating circuit; measuring a value indicative of a temperature of the aerosol-forming substrate; and controlling the temperature of the aerosol-forming substrate by changing a parameter or configuration of the aerosol-generating device based on the measured value.

Example Ex146. The method according to Ex145, wherein the method is adapted according to any one of the Examples Ex46 to Ex84.

Example Ex147. An aerosol-generating system comprising: an aerosol-generating article comprising an aerosol-forming substrate and an aerosol-generating device for dielectrically heating the aerosol-forming substrate, the aerosol-generating device comprising: a power source; an oscillation circuit including a resonant feedback circuit and a switching unit powered by the power source forming a self-oscillating circuit; a dielectric heating element fed by the oscillation circuit, the dielectric heating element being a capacitor for the resonant feedback circuit, the dielectric heating element being arranged for heating the aerosol-forming substrate by dipole rotation when subjected to an alternating electric field caused by the dielectric heating element; a temperature determining unit for measuring a value indicative of a temperature of the aerosol-forming substrate; and a controller for controlling the temperature of the aerosol-forming substrate by changing a parameter or configuration of the aerosol-generating device based on a signal from the temperature determining unit.

Example Ex148. The system according to Example Ex147, wherein the system is adapted according to any one of the Examples Ex86 to Ex141 .

Brief Description of Drawings

The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a schematic illustration of a dielectric heating aerosol-generating system according to embodiments of the disclosure; Figure 2 is a schematic illustration of an oscillation circuit for use in the dielectric heating aerosol-generating system of Figure 1 , according to embodiments of the disclosure;

Figure 3A is a schematic illustration of an oscillation circuit showing two different phaseshifting elements, one exemplarily implemented as a resonance circuit, one exemplarily implemented as a capacitive element, to achieve a 180° phase shift;

Figure 3B is a schematic illustration of an oscillation circuit showing two different phaseshifting elements, one exemplarily implemented as a resonant circuit having parallel resonance properties, one exemplarily implemented as a capacitive element, to achieve a 180° phase shift;

Figure 3C is a schematic illustration of an oscillation circuit having a resonant cavity;

Figure 4 illustrates an oscillation circuit diagram according to embodiments of the disclosure;

Figure 5A-F illustrate how a Quartz-mimicking or Quartz equivalent circuit may be derived, as a non-limiting example of a parallel-resonant circuit, according to embodiments of the disclosure;

Figure 6 illustrates a frequency analyzer plot of a parallel resonant circuit showing the effect of the switching frequency on the phase shift and impedance of a parallel resonant circuit;

Figures 7A-C are isometric illustrations of inductor pairs sharing a mutual inductive coupling for use in the oscillation circuit of Figures 2 to 4, according to embodiments of the disclosure;

Figures 8A-D are isometric and schematic illustrations of flat interdigitated electrode arrangements for use in the oscillation circuit of Figures 2 to 4, according to embodiments of the disclosure;

Figure 9 shows an isometric and schematic illustration of a tubular interdigitated electrode arrangement for use in the oscillation circuit of Figures 2 to 4 configured to dielectrically heat an aerosol-forming substrate 110, according to embodiments of the disclosure;

Figure 10 shows a schematic illustration of an interdigitated electrode arrangement with a varying electrode separation distance, according to embodiments of the disclosure;

Figures 11A-D show isometric and schematic illustrations of tubular interdigitated electrode arrangements for use in the oscillation circuit of Figures 2 to 4 configured to dielectrically heat an aerosol-forming substrate 110;

Figure 12 is a schematic illustration of a temperature sensing system for detecting a temperature of an aerosol-forming substrate situated with the electrode arrangement, according to embodiments of the disclosure;

Figure 13 is a schematic illustration of an electrode arrangement and two inductively coupled inductors formed on a quartz glass substrate, according to embodiments of the disclosure;

Figure 14 is a schematic illustration of a temperature sensing system for detecting a temperature of an aerosol-forming substrate situated with the electrode arrangement, according to embodiments of the disclosure; Figure 15 is a schematic illustration of a control system utilizing a temperature sensing system for controlling the power delivered to an aerosol-forming substrate based on a detected aerosol-forming substrate temperature;

Figure 16 is a schematic illustration of a control system utilizing a temperature sensing system for controlling the power delivered to an aerosol-forming substrate based on a detected aerosol-forming substrate temperature, according to a further embodiment of the disclosure;

Figure 17 is an alternative schematic illustration of an oscillation circuit for use in the aerosolgenerating system of Figure 1 , according to embodiments of the disclosure;

Figure 18 is a schematic illustration of a control system utilizing a frequency sensing system for controlling the power delivered to an aerosol-forming substrate based on a frequency of an alternating electric field detected across an electrode assembly, according to embodiments of the disclosure.

Specific Description

The above and other features and advantages of example embodiments will become more apparent by describing in detail, example embodiments with reference to the attached drawings. However, specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments. Example embodiments may, however, be embodied in many alternate forms and should not be construed as limited to only the embodiments set forth herein.

Accordingly, while example embodiments are capable of various modifications and alternative forms, embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit example embodiments to the particular forms disclosed, but to the contrary, example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of example embodiments. Like numbers refer to like elements throughout the description of the figures.

Figure 1 is a schematic illustration of a dielectric heating aerosol-generating system 100 according to an embodiment of the disclosure. The system 100 comprises an article 105 comprising an aerosol-forming substrate 110 and an aerosol-generating device 120 for heating the aerosolforming substrate 110. The aerosol-generating device 120 comprises a first electrode 130 and a second electrode 135 separated by a cavity 140 for receiving the article 105. The cavity 140 and the article 105 are sized such that the aerosol-forming substrate 110 is in contact or in close proximity to both the first electrode 130 and the second electrode 135 when received within the cavity 140. Moreover, the first electrode 130 and the second electrode 135 form part of a feedback loop of an oscillation circuit 150 via a first and second electrical contact 160, 165.

In other examples, the first electrode 130 and the second electrode 135 may form part of the article 105 comprising the aerosol-forming substrate 110. In such embodiments, a cavity between the first and second electrical contacts 160, 165 is sized such that, when the aerosol-forming article 105 is housed within the cavity 140, an electrical connection is made between the first electrode 130 and the first electrical contact 160, and the second electrode 135 and the second electrical contact 165.

In some embodiments, the width of the article 105 comprising the aerosol-forming substrate 110 is slightly greater than the spacing between the first electrode 130 and the second electrode 135, such that the distal end of the aerosol-generating substrate 110 is slightly compressed between the first electrode 130 and the second electrode 135. In some embodiments, the article 105, in an initial, uncompressed form has a width between 5-30% larger than the distance between the first electrode 130 and the second electrode 135. This may reduce or prevent the build-up of air between the first electrode 130 and the second electrode 135 when the aerosol-forming article 105 is received in the cavity 140, and decrease a distance between first and second electrodes 130, 135 for dielectric heating, thereby improving dielectric properties of the load capacitor CL and the accuracy of any measurements or determinations of the dielectric properties of the aerosol-forming substrate 110 performed by the aerosol-generating device 120.

The aerosol-forming substrate 110 may comprise tobacco-based or non-tobacco based materials having an aerosol forming material therein and one or more active agents or ingredients, such as nicotine, pharmaceutical, botanicals, flavorants, liquid substrates with one or more active agents or ingredients, or a combination thereof. The aerosol-forming substrate 110 can also be a liquid aerosol-forming substrate and thereby the aerosol-forming article 105 can be in the form of a cartridge, capsule, or liquid container, and the electrodes 130, 135 can be configured as a wicking element or capillary element for liquid transfer. For example, it is possible that first and second electrodes 130, 135 form a capillary structure that is part of the aerosol-forming article 105 or reaches into an inner volume of the aerosol-forming article 105 that can heat and vaporize a liquid aerosolforming substrate 110 located in the inner volume. For example, the first and second electrodes 130, 135 can be embodied as parallelly arranged plates separated by a distance that forms a capillary channel, for example in a range between 0.1 mm to 2 mm, depending on the desired capillary strength or rise. The first and second electrodes can be arranged as two matrices or arrays of pinlike, rod-like, or tab-like electrodes with opposite polarity, the two matrices or arrays interposed between each other, forming a capillary structure therebetween, for example with an average distance between neighboring pin-like electrodes being in a range between 0.1 mm to 2 mm, depending on the desired capillary strength or rise. In another variant, the wicking element can be a separate element that is interposed between two electrodes 130, 135, for example flat or slightly curved electrodes 130, 135.

The aerosol-generating device 120 further comprises a power supply 170 and a controller 180 electrically coupled to the oscillation circuit 150. In this embodiment, the power supply 170 can be a rechargeable lithium ion battery, for example with one or more lithium ion battery cells, and the aerosol-generating device 120 comprises a power connector that enables the aerosol-generating device 120 to be connected to a mains power supply for recharging the power supply. Providing the aerosol-generating device 120 with a power supply, such as a battery, enables the aerosolgenerating device 120 to be portable and used outdoors or in locations in which a mains power supply is not available.

In use, power is supplied to the oscillation circuit 150 from the power supply 170 when a user activates the aerosol-generating device 120. In this embodiment, the aerosol-generating device 120 is activated by a user pressing an activation button (not shown) that can be provided on an external surface of the aerosol-generating device 120. It will be appreciated that in other embodiments, the aerosol-generating device 120 may be activated in another manner, such as on detection of a user drawing on a mouthpiece (not shown) by a puff sensor provided on the mouthpiece, or a user holding the aerosol-generating device 120. When power is supplied to the oscillation circuit 150, the oscillation circuit 150 generates an alternating electric field across the first and second electrodes 130, 135 to dielectrically heat the aerosol-forming substrate 110 in the cavity 140, releasing volatile compounds.

The controller 180 may cause dielectric heating of the aerosol-forming substrate 110 that is located between the two electrodes 130, 135 with an average dielectric heating power density in a range between 1W/cm³ to 25W/cm³, preferably between 1.5W/cm³ and 15W/cm³ per volume of substrate material during a time period of less than 15 minutes. In particular, during a heat-up phase, the average dielectric heating power density may be controlled or set to be in a range between 7W/cm³ to 25W/cm³, preferably between 8W/cm³ to 20W/cm³. During a target heating phase (also called maintenance heating phase) during consumption, the average dielectric heating power density is in a range between 1W/cm³ to 7W/cm³, preferably between 1W/cm³ to 5W/cm³. In a nonlimiting example, these power densities may be used in heat-not-burn (HnB) applications.

In yet another exemplary embodiment, the aerosol-generating system 100 may be configured to provide a power density between the pair of opposing electrodes 130, 135 of between 35W/cm³ and 35kW/cm³. The aerosol-generating system 100 may be configured to provide a power density between the pair of opposing electrodes 130, 135 of between 50W/cm³ and 10 kW/cm³, between 50W/cm³ and 2.5kW/cm³ or between 50W/cm³ and 1 ,25kW/cm³. The aerosol-generating system 100 may be configured to provide a power density between the pair of opposing electrodes 130, 135 of between 170W/cm³ and 2.5kW/cm³, between 250W/cm³ and 2.5kW/cm³ or between 500W/cm³ and 2.5kW/cm³. Preferably, the aerosol-generating system 100 may be configured to provide a power density between the pair of opposing electrodes 130, 135 of between 1 kW/cm³ and 2kW/cm³. In a non-limiting example, these power densities may be used for heating and vaporizing liquids during a puff in a puff-on-demand application, for example for a duration in a range between 0.5 seconds to 10 seconds.

For such puff-on-demand applications, the dielectric heating losses per volume may be substantially higher than the ones of HnB applications with minute-long heating sessions. However, the heated volume may be smaller (~10 mm³ in puff-on-demand applications versus -300 mm³ in HnB applications).

The aerosol-generating system 100 is also configured for measuring a dielectric property of the aerosol-forming article 105 or the aerosol-forming substrate 110 using the electrodes 130, 135 that are employed for dielectric heating of the aerosol-forming substrate 110. In some examples, the first and second electrodes 130, 135 can be used for dielectric measurements, either during the heating process or separately to the heating process. In this embodiment, the aerosol-generating system 100 can be configured to determine the presence of the aerosol-forming article 105 between the first electrode 130 and the second electrode 135. The aerosol-generating system can be configured to measure a dielectric property, for example an instant value, timely-evolution, or change of a dielectric property, for example to determine whether the aerosol-forming article 105 meets specific criteria or is an authentic substrate. The aerosol-generating system in this example is also configured to control the heating of the aerosol-forming substrate 110 based on the measured dielectric property of the aerosol-forming article 105.

In one exemplary embodiment, the material composition of the substrate 110 of the aerosolforming article 105 that can be dielectrically heated by the aerosol forming device 100 can include tobacco powder or tobacco cut filler.

As used herein, the term “cut filler” is used to describe to a blend of shredded plant material, such as tobacco plant material, including, in particular, one or more of leaf lamina, processed stems and ribs, homogenised plant material. Preferably, the cut filler comprises at least 25 percent of plant leaf lamina, more preferably, at least 50 percent of plant leaf lamina, still more preferably at least 75 percent of plant leaf lamina and most preferably at least 90 percent of plant leaf lamina.

The cut filler suitable to be used with the present invention generally may resemble cut filler used for conventional smoking articles. The cut width of the cut filler preferably is between 0.3 millimeters and 2.0 millimeters, more preferably, the cut width of the cut filler is between 0.5 millimeters and 1 .2 millimeters and most preferably, the cut width of the cut filler is between 0.6 millimeters and 0.9 millimeters.

The aerosol-generating substrate 110 may comprise between 80 milligrams and 400 milligrams of cut filler. For example, the aerosol-generating substrate 110 may comprise between 100 milligrams and 300 milligrams of cut filler, between 100 milligrams and 250 milligrams of cut filler, between 125 milligrams and 200 milligrams of cut filler, or between 140 milligrams and 180 milligrams of cut filler, such as about 150 milligrams of cut filler.

The aerosol-forming substrate 110 of the aerosol-forming article 105 may comprise an aerosol former. Where the aerosol-forming substrate 110 comprises cut filler, the cut filler may be soaked with aerosol former. Soaking the cut filler can be done by spraying or by other suitable application methods. Preferably, the aerosol former comprises one or more of glycerine and propylene glycol (PPG). The aerosol former may consist of glycerine or propylene glycol or of a combination of glycerine and propylene glycol. The aerosol-forming substrate 110 may comprise any amount of aerosol former. For example, the aerosol-forming substrate 110 may comprise between 5 weight percent aerosol former and 25 percent aerosol former. For example, the aerosol-forming substrate 110 may comprise between 10 weight percent aerosol former and 20 percent aerosol former, or between 15 weight percent aerosol former and 20 percent aerosol former. Preferably, the aerosolgenerating substrate 110 comprises about 18 weight percent aerosol former. The weight percentages of aerosol former are given as a dry weight basis of the cut filler, with the balance being tobacco.

The aerosol-forming substrate 110 may have a density of no more than 0.45 grams per cubic centimetre, no more than 0.4 grams per cubic centimetre, no more than 0.36 grams per cubic centimetre, no more than 0.3 grams per cubic centimetre, or no more than 0.25 grams per cubic centimetre. The aerosol-forming substrate 110 may have a density of at least 0.1 grams per cubic centimetre. For example, the aerosol-forming substrate 110 may have a density of at least 0.15 grams per cubic centimetre, at least 0.2 grams per cubic centimetre, or at least 0.28 grams per cubic centimetre.

The aerosol-forming substrate 110 may be cylindrically shaped, and is preferably substantially cylindrically shaped, having a length of between 10 mm and 15 mm, such as between 11 mm and 14 mm, preferably about 12 mm, and having a diameter of between 4.5 mm and 8 mm, such as between 6.5 mm and 7.5 mm, preferably about 7 mm.

Suitable aerosol-forming substrates and articles comprising cut filler include those described in W02022/074240 and/or W02022/074158, these references herewith incorporated by reference in their entirety.

In another exemplary embodiment, the material composition of the aerosol-forming substrate 110 of the aerosol-forming article 105 that can be dielectrically heated by the aerosol forming device 100 can include reconstituted tobacco, such as one or more sheets of homogenized tobacco material made by a cast leaf process.

Where the aerosol-forming substrate 110 comprises homogenised tobacco material, the tobacco material preferably comprises particulate tobacco obtained by grinding or otherwise comminuting tobacco leaf lamina. Such homogenised tobacco material may have a tobacco content of at least about 40% by weight on a dry weight basis or of at least about 50% by weight on a dry weight basis. In other embodiments, the homogenised tobacco material may have a tobacco content of about 70% or more by weight on a dry weight basis, such as between 70% and 80% by weight on a dry weight basis.

The aerosol-forming substrate 110 may comprise one or more intrinsic binders, that is tobacco endogenous binders, one or more extrinsic binders, that is tobacco exogenous binders, or a combination thereof to help agglomerate the particulate tobacco. Alternatively, or in addition, the aerosol-forming substrate 110 may comprise other additives including, but not limited to, tobacco and non-tobacco fibres, aerosol-formers, humectants, plasticisers, flavorants, fillers, aqueous and non-aqueous solvents and combinations thereof.

Suitable extrinsic binders for inclusion in the aerosol-forming substrate 110 are known in the art and include, but are not limited to: gums such as, for example, guar gum, xanthan gum, arabic gum and locust bean gum; cellulosic binders such as, for example, hydroxypropyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose and ethyl cellulose; polysaccharides such as, for example, starches, organic acids, such as alginic acid, conjugate base salts of organic acids, such as sodium-alginate, agar and pectins; and combinations thereof. For example, the aerosol-forming substrate 110 may comprise between 1% and 5% extrinsic binder by weight on a dry weight basis, such as between 1.5% and 3.5% extrinsic binder by weight on a dry weight basis, preferably about 2% extrinsic binder by weight on a dry weight basis. Preferably, the extrinsic binder is guar gum.

Suitable non-tobacco fibres for inclusion in the aerosol-forming substrate 110, to strengthen the material, are known in the art and include, but are not limited to: cellulose fibers; soft-wood fibres; hard-wood fibres; jute fibres and combinations thereof. For example, the aerosol-forming substrate 110 may comprise between 2% and 6% non-tobacco fibres by weight on a dry weight basis, such as between 3% and 5% non-tobacco fibres by weight on a dry weight basis, preferably about 4% non-tobacco fibres by weight on a dry weight basis. Preferably, the non-tobacco fibres are cellulose fibres.

The aerosol-forming substrate 110 may comprise an aerosol former. Preferably, the aerosol former comprises one or more of glycerine and propylene glycol. The aerosol former may consist of glycerine or propylene glycol or of a combination of glycerine and propylene glycol. The aerosolforming substrate 110 may comprise any amount of aerosol former. For example, the aerosolforming substrate 110 may comprise between 5 weight percent aerosol former and 25 percent aerosol former. For example, the aerosol-forming substrate 110 may comprise between 10 weight percent aerosol former and 20 percent aerosol former, or between 15 weight percent aerosol former and 20 percent aerosol former. Preferably, the aerosol-forming substrate 110 comprises about 18 weight percent aerosol former. The weight percentages of aerosol former are given as a dry weight basis of the aerosol-forming substrate 110.

Preferably, the aerosol-forming substrate 110 has a weight of between 220 milligrams and 350 milligrams. For example, the aerosol-forming substrate 110 may have a weight between 240 milligrams and 320 milligrams, between 250 milligrams and 310 milligrams, between 240 milligrams and 280 milligrams, or between 290 milligrams and 330 milligrams.

The aerosol-forming substrate 110 may have a density of no more than 0.75 grams per cubic centimetre, no more than 0.68 grams per cubic centimetre, no more than 0.67 grams per cubic centimetre, no more than 0.59 grams per cubic centimetre, or no more than 0.56 grams per cubic centimetre. The aerosol-forming substrate 110 may have a density of at least 0.5 grams per cubic centimetre. For example, the aerosol-forming substrate 110 may have a density of at least 0.55 grams per cubic centimetre, at least 0.56 grams per cubic centimetre, or at least 0.64 grams per cubic centimetre.

The aerosol-forming substrate 110 may be cylindrically shaped, and is preferably substantially cylindrically shaped, having a length of between 10 mm and 15 mm, such as between 11 mm and 14 mm, preferably about 12 mm, and having a diameter of between 4.5 mm and 8 mm, such as between 6.5 mm and 7.5 mm, preferably about 7 mm, and can preferably have substrate volumes in a range between 0.16 cubic centimeters to 0.75 cubic centimeters.

In yet another exemplary embodiment, the aerosol-forming substrate 110 can be a non- tobacco-based substrate and/or a substantially tobacco free substrate. The aerosol-generating substrate 110 may be a cellulose-based substrate, for example as described in W02020/207733, WO2023/ 126494, and/or WO2022/248378, these references herewith incorporated by reference in their entirety.

Figure 2 is a schematic illustration of an oscillation circuit 250 for use in the aerosolgenerating system 100 of Figure 1 , according to an embodiment of the disclosure. Oscillation circuit 250 comprises a switching unit 260 interconnected with a resonator feedback loop 270 to provide for a self-oscillating signal to the switching unit 260. The feedback loop 270 is connected between an input and an output of the switching unit 260. The switching unit 260 comprises a single transistor, such as a bipolar junction transistor (BJT) or a field effect transistor (FET).

The oscillation circuit 250 can further comprise a choke 280 that acts on an input to the feedback loop 270 to provide for a stimulation signal, for example a stimulation voltage. The oscillation circuit also comprises a biasing unit 290 acting on the feedback loop 270 for providing a variable or controllable biasing signal, for example a biasing voltage for setting the operating conditions. In the variant shown, the feedback signal can be described as a voltage. The output voltage UOUT of the switching unit 260 is coupled to the feedback loop 270 providing a feedback switching signal in the form of a voltage UIN to the switching unit 260. The configuration of the feedback loop 270 is such that the output signal, e.g. the voltage UOUT of the switching unit 260 can undergo a phase change and arrives inverted at the input UIN of the switching unit 260 for resonant oscillation. In other configurations, a current could be used as the feedback signal with a switching unit 260 comprising a BJT.

The feedback loop 270 is configured to be self-oscillating and will oscillate at or close to a given resonance frequency determined by the values of the passive components of the feedback loop 270. Feedback loop 270 is configured to provide a 180° phase shift from the output UOUT to input UIN of switching unit 260 for oscillation, and in addition, the transistor T is configured for inverting operation. As shown in Figures 3a and 3b, feedback loop 270 includes a resonant circuit 272 comprising the load capacitor CL providing for a first 90° phase shift or quarter wave shift to the feedback signal. Feedback loop 270 further includes a capacitive element 274 providing for a second 90° phase shift or quarter wave shift to the feedback signal, such that the feedback signal reaching the input of the switching unit 260 is inverted and phase-shifted by 180°. Switching unit 260 is itself configured for inverted switching operation to provide a 180° phase shift between the input UIN and the output UOUT of the switching unit 260.

Resonant circuit 272 comprises the first and second electrodes 130, 135, together forming a load capacitor CL. When an aerosol-forming substrate 110 is situated between the first and second electrodes 130, 135, it forms part of the load capacitor CL. Importantly, the load capacitor CL is formed in the feedback loop 270, and not at a separate output or part of a separate circuitry that is connected to the switching unit 260. This enables a high-frequency oscillating voltage to be created across the electrodes of load capacitor CL, which is needed for sufficient and efficient dielectric heating of the aerosol-forming substrate 110, without having an additional output or circuit to the already resonating feedback loop 270, which would create unnecessary losses and circuit complexity. The resonant circuit 272 may comprise a series resonator circuit or a parallel resonator circuit, examples of which are described in greater detail below.

In an alternative embodiment, resonant circuit 272 may include a resonant cavity 272, as illustrated in Figure 3C. The resonant circuit 272 including resonant cavity may have an interior volume configured to receive an aerosol-forming substrate 110, for example having an opening for inserting an aerosol-forming substrate 110. In an example, the resonant circuit 272 including resonant cavity can be configured as a A/4 resonator. The resonant circuit 272 including resonant cavity may be configured to behave like an RLC circuit. The inductor L and the capacitor C are arranged in parallel to each other, to have a parallel resonance or a frequency close to the parallel resonance that can be stimulated by the switching unit 260. Resonant circuit 272 including cavity may be coupled to the feedback loop 270 using one or more of a capacitive coupling, an inductive antenna coupling (magnetic coupling), a direct electric coupling, or a window coupling (e.g. coupling with a loop).

The resonant circuit 272 including resonant cavity can have any shape, but preferably has a cylindrical shape or a rectangular parallelepiped shape. In one embodiment, the resonant cavity can be configured as a split-ring resonator.

Figure 4 illustrates an oscillation circuit 350 according to a non-limiting, exemplary embodiment of the disclosure. Oscillation circuit 350 comprises a switching unit 260 in the form of a transistor T having an intrinsic capacitance 0. Moreover, transistor T is configured for inverting operation, for example as an inverting common source FET, MOSFET, or a common emitter BJT. The source terminal of transistor T can be coupled to a DC power supply via a choke 280. Between the gate and source terminals of transistor T extends a feedback loop 270. The feedback loop 270 comprises a resonant circuit 272 including a load capacitor CL having a first and second electrode 130, 135 separated by an aerosol-forming substrate 110. In the variant shown, the resonator circuit 272 is also connected to ground via a delay line DL and a capacitor C2 connected in series to the delay line DL. The circuit 350 further comprises a biasing unit 290 coupled to the gate terminal of the transistor T via the delay line DL. AS shown in Figure 4, the biasing unit 290 is electrically connected between the delay line DL and the capacitor C2, so that the biasing unit 290 is somewhat isolated from the high oscillation frequency of the feedback loop 270. The delay line could be placed elsewhere, for example somewhere else in the feedback loop.

The delay line DL is a time delay element, for example an element that has inductive behavior, for slowing down the arriving voltage wave from the feedback loop 270 during a period of the oscillation. This allows to tune the resonant circuit 272 to a desired switching and oscillation frequency, to move the oscillation frequency away from the natural resonant frequency given by the resonant circuit 272. This ensures that oscillation circuit 350 remains in a predefined frequency operating range to provide for the requisite inverted or 90° phase shifted feedback and also to make sure that the feedback loop has a low impedance to provide for a high gain, as described in greater detail below.

The oscillation circuit 350 is shown with electrical contacts 160, 165 that are arranged on each side of the load capacitor CL. In some embodiments, the first and second electrodes 130, 135 may be removable from the oscillation circuit 350, or may form part of the aerosol-forming article 110. In such embodiments, electrical contacts 160, 165 provide an electrical connection between the first and second electrode 130, 135 and the feedback loop 270. In embodiments where the load capacitor CL is fixed within the feedback loop 270, for example, such that an aerosol-forming substrate 110 can be inserted and removed to and from a cavity formed in between the first and second electrodes 130, 135, electrical contacts 160, 165 provide electrical connections from the first and second electrodes to the next components in the feedback loop 270, e.g. inductors Li and L2.

With respect to the power supply voltage, a DC power supply voltage is provided, that is preferably in a range that is suitable for battery operation with one or more standard battery cells. Preferably, the DC power supply voltage is below 14V. For example, it is possible to operate the oscillation circuit 350 on a single battery cell, for example an 18650 battery cell (Li-Ion), or a similar battery cell, that provides for 3.2V to 3.9V. However, more preferably, a voltage of one battery cell of an exemplary 3.5V to 7V for power supply can be boosted, for example by a DC-DC converter (e.g. a boost circuit), or a voltage doubler. Alternatively or in addition, two or more battery cells can be used in series, or other configurations or arrangements that allows to increase a voltage from one or more battery cell can be used. It is also possible to have a controllable output voltage (e.g. DC- DC converter, voltage regulator), to control the temperature of heating by a change to the DC supply voltage, or to boost the voltage (for example to 10-12V) for maximum power at the preheating stage, to speed up the preheating stage with the goal to reach the aerosolization temperature quickly. Control of the DC supply voltage is one way that makes it possible to rapidly change heating power despite the oscillation circuit 350 freely oscillating.

A capacitor Ci is arranged in parallel to the transistor T and therefore in parallel with the intrinsic capacitor of the transistor T (e.g. a field effect transistor). This facilitates a less voltagedependent oscillation and frequency, stabilizes the oscillation, and also improves the overall dielectric heating efficiency. Capacitance of capacitor Ci is chosen to be larger than the maximal intrinsic capacitor Ci of transistor T at the operating conditions, so that the variation of the intrinsic transistor based on frequency, temperature, etc. has much less or negligible influence on the feedback loop 270. For example, in a non-limiting embodiment, the value can be in a range between 2pF to 100pF, more preferably in a range between 5pF and 50pF.

Capacitive element 274 comprises a capacitor C2 arranged at the output or end of the resonant circuit 272. In one embodiment, capacitive element 274 comprises more than one capacitor. As described above, capacitive element 274 has the function of providing a 90° phase shift to the feedback voltage of feedback loop 270 with minimized losses or other undesired effects, and it therefore needs to have a high-quality factor or Q factor, preferably above 1000 at 100MHz. The capacitance value for C2 of the capacitive element 274 should be relatively high as compared to Ci, for example in a range between 500pF to 100nF, more preferably between 1nF and 50nF, which leads to a low impedance of capacitive element 274. In a variant, the capacitive element 274 can be implemented as a RC network to provide for the 90° phase shift, for example using two single- resistor-capacitor networks, having two capacitors in the feedback loop, each capacitor connected to ground via a resistor.

Resonant circuit 272, together with capacitive element 274, provides for a 180° phase shift and a voltage gain from the output UOUT to the input UIN, and transistor T (for example a FET) is configured for inverting operation, thereby also providing for another 180° phase shift. This results in a resonant or close-to resonant oscillation and an amplified voltage UL across the electrodes 130 and 135 of the load capacitor CL, as compared to the DC supply voltage. When operating close to resonance, the resonant circuit 272 circuit behaves inductively, having a high Q factor. Furthermore, the feedback loop 270 is impedance-matched with the transistor T, at an impedance of approximately 500mQ to 8Q, preferably around 2Q, to provide for a high gain, leading to an increased voltage across the load capacitor CL. Also, preferably, this gain is achieved without the use of an additional voltage or current amplifying passive element, such as a tapped inductor or a transformer located in the circuit that forms the feedback loop 270, as such passive elements are difficult and lossy to operate and design at frequencies greater than 50 MHz. Preferably, the impedances of the resonant circuit and capacitor C2 add up to match the impedance of the transistor T, more preferably the resonant circuit is substantially impedance-matched with the transistor.

The combination of capacitor Ci , the feedback loop with resonant circuit 272 and capacitive element 274 can also be described as a bandpass filter or Pi or TT network that generates a 180° phase shift. In the illustrated embodiment, the resonant circuit 272 of the feedback loop 270 is not connected to ground, but is suspended with ends at each capacitor Ci and C2, thereby not having a direct ground connection at either end of resonant circuit 272, reducing stray elements and ground influences for more predictable operation.

At the operating frequency, the resonant circuit 272 including load capacitor CL acts as an inductive load providing a first 90° phase shift, also referred to as a quarter-wave phase shift, and capacitive element 274 exemplarily including a high quality factor capacitor C2 connected to ground, provides for the second 90° phase shift or quarter-wave phase shift.

Oscillation circuit 350 can be described or characterized as a Pierce oscillation circuit with a modified feedback loop 270, where the physical Quartz element is replaced by a Quartz-mimicking or Quartz electric equivalent circuit to provide for an inverting feedback to the switching unit 260 that also operates in an inverted mode. In some embodiments, oscillation circuit 272 can be based on other resonant feedback loop oscillation circuit configurations, for example, but not limited to, the use of a Colpitts or Hartley type oscillator, using an inverting transistor T.

Figures 5A to 5F illustrate how a Quartz-mimicking or Quartz equivalent circuit may be derived using a variant of a parallel resonator circuit PRC, that can serve as an exemplary and nonlimiting embodiment as resonant circuit 272. A Quartz-mimicking or Quartz equivalent circuit can have a parallel resonance at a given frequency. This can be seen as a circuit with two branches, one representing the mechanical oscillation and one representing the electric behavior, as illustrated in figure 5A and 5B. The mechanical oscillation is represented by a first branch having load capacitor CL and an inductor LTOT. The electric oscillation is represented by a second branch arranged in parallel to the first branch, having a Capacitor CE. This configuration leads to a series connection of two capacitors CL and CE (seen around the loop formed by the two branches) so that CE will decrease the overall capacitive value of the equivalent circuit. Also, this circuit provides an inductive phase shift of about 90° within certain defined frequency range.

Referring now to Figure 5C, one branch of the parallel resonator circuit PRC comprises an inductor LTOT and the load capacitor CL connected in series of the first branch. This branch can be improved by splitting LTOT into two inductors Li and L2 on each side of the load capacitor CL, as shown in Figure 5D, to provide a split inductor or split-coil design and a more symmetric application of the voltage UL across the load capacitor CL, thereby improving dielectric heating efficiency. To provide for parallel resonance, the capacitor CE of the second branch can be replaced with an inductor (as shown in Figure 5F) due to capacitor CE‘S minimal capacitive effect on CL.

In a non-limiting example starting from the split inductor Li and L2 of the resonant circuit of Figure 5D, inductors Li and L2 can be mutually magnetically coupled to form a mutual inductance M, thereby forming the parallel circuit branch or second branch of the resonant circuit 272, as shown in Figure 5E. The mutual magnetic coupling can be achieved by the close proximity of the two inductors Li and L2 with alignment of winding axis of the coils, or by use of a mutual magnetic core, or both. This has the advantage of providing a parallel-resonator circuit PRC without the use of additional wires for the second branch, and without additional windings or separate magnetic cores for a second parallelly-arranged inductor. This also allows for a symmetric arrangement that favors and facilitates the inductive coupling of the two inductors Li, L2 and the balancing of the voltage UL over load capacitor CL. The symmetry of the two branches in either direction with first branch Li - CL - L2 and the second branch with inductor LE, representing the two mutual inductance values, facilitates the symmetrical balancing of the voltage over the electrodes of the load capacitor CL, which consequently reduces losses created at the load capacitor CL. This split inductor principle can also be referred to as a split coil resonator.

The resonant circuit 272 could also be implemented as shown in the Figure 5F, where the mutual inductance M (seen two times due to the mutuality) is replaced by a separate inductive element, for example inductor LE.

The values of components in this resonant circuit 272 are preferably chosen to be in the following exemplary and non-limiting ranges. LTOT can be a range between 10nH to 50nH, more preferably between 15nH and 40nH, which is the equivalent of Li plus L2, E could be in a range between 7nH and 30nH, more preferably between 10nH and 20nH, and the value of the load capacitor can be in a range between 0.5pF to 5pF, more preferably between 1 pF to 3pF.

The resonant circuit 272 can be configured as another type of tank circuit providing for the 90° phase shift in a given frequency range. In one embodiment, the resonant circuit 272 can be implemented as a series resonant circuit, having the load capacitor CL connected in series with one or more inductive elements, configured to provide for an inductive response or 90° phase shift in a given frequency range that is suitable for dielectric heating.

To have a proper inverting effect and a 180° phase shift on the feedback loop 270 between UIN and UOUT, the oscillation circuit 350 must remain in a frequency operating range where the behavior of the feedback loop 270 is highly inductive. In the example comprising a parallel resonator circuit (PRC), the series resonance frequency fsER is relatively close to the parallel resonance frequency f_PAR. If the oscillation frequency fs of the PRC exceeds the parallel resonance frequency fpAR, the feedback loop 270 will act capacitively and not provide the necessary phase inversion to the loop 270. Furthermore, the equivalent impedance of the circuit will increase to an extent that is too high for efficient dielectric heating as not providing for the requisite gain.

Oscillations in the feedback loop 270 will be naturally drawn towards the parallel resonance frequency of the resonant circuit 272. However, the addition of a delay line DL can introduce a slight time delay limiting the oscillation frequency below the parallel resonance frequency. Figure 6 shows a frequency analyzer plot of an exemplary resonant circuit 272, specifically a plot of a parallel resonator circuit PRC showing the relationship between the oscillation frequency (with a series resonance at 855 MHz and a parallel resonance at 1.246 GHz), the phase shift across the PRC (with a relatively flat inductive 90° frequency response between the two resonant frequencies) and the effective impedance of the PRC. More specifically, it can be seen from Figure 6 that the 90° phase shift starts dropping before the parallel resonance frequency fpAR is reached. After the parallel resonance frequency f_PAR, the phase shift response drops below 0° to capacitive behavior and the impedance is very high, e.g. 2.4kQ. The ideal operating frequency range is closer to the series resonance frequency fsER where the phase shift is still 90° and the impedance response is low, preferably an impedance that is less than 20, more preferably less than 10. The parallel resonance frequency f_PAR can be above 1GHz, e.g. 1GHz to 1.5GHz, while the actual switching frequency fs can be below 1GHz, and this lower switching frequency is caused by the delay line DL.

Ideally, the oscillation frequency fs should be set to be below the parallel resonance frequency f_PAR but above the series resonance frequency fsER, to make sure that two conditions are fulfilled, firstly (i) that the resonant circuit behaves inductively to provide a 90° phase shift, and secondly (ii) to make sure that the impedance of the resonant circuit (an therefore the feedback loop 270) is low, as illustrated in the graphs of FIG. 6. For example, a resulting impedance of the feedback loop at the oscillation frequency fs of the oscillation circuit can be in a range of approximately 10OmQ to 2Q. Preferably, the delay line DL is configured such that the oscillation frequency fs is closer to the series resonance frequency fsER than to the parallel resonance frequency f_PAR, thereby maintaining a low resonant circuit impedance while operating at a frequency range where the resonant circuit provides the 90° phase shift. The time delay caused by delay line DL needs to be relatively short, as the series resonance and the parallel resonance of a parallel oscillating circuit PRC are close to each other, relative to the overall frequency range. Preferably, the delay caused by delay line DL that acts of feedback loop 270 should be in a range between 5% to 35% of the period of the parallel resonance frequency f_PAR, providing that the above two conditions (i) and (ii) are fulfilled. In an embodiment, the delay caused by the delay line DL that acts on feedback loop 270 is in a range between 35% and 90% of a difference between the period of the parallel resonance frequency f_PAR and the period of the series resonance frequency fsER, again providing that the above two conditions (i) and (ii) are fulfilled, more preferably a range between 50% and 85%. For example, taking the illustration of FIG. 6 and as a non-limiting numerical example, assuming that a parallel resonance frequency is at 1.25 GHz, therefore having a period of 800ps (picoseconds), and a series resonance is at 855MHZ, and therefore a period of 1169ps, there is a difference of 369ps between the period of f_PAR and fsER. The time delay caused by delay line DL can be in the above range, for example at 70% of the period difference between f_PAR and fsER, thereby being 258ps, thereby making sure that the feedback loop 270 has the desired inductive behavior and low impedance that is necessary to provide inverting feedback at high gain.

Preferably, the delay line is implemented as a meandering conductive element having dominantly inductive behavior, for example a meandering element having from two (2) to twelve (12) meandering branches, more preferably from three (3) to eight (8) meandering branches. Such implementations exhibit minimal stray inductive and capacitive behavior. Various delay line structures can be used to provide the desired function, for example an Omega-shaped coil, single planar coil, flat inductor, wavy line, zig-zag line, or a sawtooth line. It is also possible to provide the required delay line functionality by a specific transmission line design. For example, it is possible that the physical element of the delay line DL is implemented as a conductor in a printed circuit board, for example implemented as a microstrip patch antenna. In some embodiments, a low-pass filter may be used as the delay line DL, however this will have an impact on the shape of the oscillating voltage, whereas a delay line DL that provides for a short time delay by inductive effect will not impact the wave shape. In the embodiment illustrated in Figure 4, delay line DL is placed between the feedback loop output of the resonant circuit 272 and capacitive element 274, but other arrangements are also possible.

Figures 7A-C are isometric illustrations of a split coil resonator having a mutual inductive coupling for use in the oscillation circuit of Figures 2 to 4, according to embodiments of the disclosure. In the example of Figure 7A, the two inductors Li and L2, are each formed as a single winding, e.g. a single loop coil. The winding central axis of each coil substantially coincides with each other, and the plane formed by each single-winding inductor is parallel to the other, and is also in close proximity. This establishes a mutual inductance between inductors Li and L2 without a magnetic core Me. If necessary, the mutual inductance M can be further increased by adding a magnetic core Me that traverses or at least partially traverses each winding of Li and L2 to reach a desired inductance level. In this respect, a distance between the two planes in which the windings are arranged can be increased, to minimize the capacitive effect between them. Preferably the windings of inductors Li and L2 are wound in the same direction around the coinciding winding central axis of, or in case a core Me is present, around the core Me or the central axis. This way, the magnetic flux caused by both coils Li and L2 is enhanced, rather than cancelled out. In other words, the two inductors Li and L2 appear as a continuously wound coil around a magnetic core Me, or around the winding central axis in case no core is used, with two winding regions forming two inductor coils Li , L2.

Figure 7B illustrates an alternative split coil resonator arrangement, wherein instead of one full loop coil for Li and L2, an omega-shaped loop is used. Other winding shapes are also possible while providing substantially the same functionality.

In some examples, it is possible to use a smaller diameter of inductor coils Li, L2, but have several loops or turns. Preferably the number of turns in each inductor coil Li, L2 is no more than five (5), preferably less than three turns, and preferably no more than one turn. To further reduce the capacitive coupling between Li and L2, the inductors Li , L2 of the split coil resonator of Figure 7B are arranged as planar coils in an omega-shape, single winding, or double winding coils, both on the same surface or plane, and are therefore not aligned in parallel to each other. This is desirable since the capacitive effect between the two inductors Li and L2 can provide for unwanted additional dielectric losses. In this embodiment, the magnetic coupling by core Me is achieved via a u-shaped core with each leg traversing a center of each planar coil Li , L2. Both Figures 7A and 7B show an embodiment of the resonant circuit 272 as a complete parallel resonant circuit PRC by virtue of the second branch being created by the mutual inductance M between inductors Li and L2.

It is also possible that the mutual inductance M between Li and L2 are created by simple proximity of the two inductor coils Li and L2, without the use of a magnetic core Me as illustrated in Figure 7C, or by inter-winding the coils of inductors Li and L2. The electrode arrangement of Figure 7C comprises parallelly arranged electrode plates E1 and E2 having curved edges to reduce hotspots in the electric field formed around the boundaries of the electrode plates.

Figures 7A and 7B illustrate electrode arrangements comprising a pair of electrode plates 130, 135 aligned in parallel, however other electrode arrangements are also possible.

Figures 8A-D are schematic illustrations of flat interdigitated electrode arrangements for use in the oscillation circuit of Figures 2 to 4, according to embodiments of the disclosure. The use of interdigitated electrodes allows for a more homogenous electric field generation, which can be used to avoid hot spots across an aerosol-forming substrate. Figure 8A shows an electrode arrangement comprising two electrodes. A first electrode comprises one or more extended portions and a second electrode comprises a corresponding one or more recessed portions for receiving the one or more extended portions of the first electrode. In other some examples, both the first and second electrodes each comprise a combination of extended portions and recessed portions configured to align with corresponding recessed portions and extended portions in the opposing electrode.

Figures 8B and 8C show electrode arrangements comprising a plurality of electrodes for each polarity wherein each electrode is positioned adjacent to electrodes of the opposite polarity.

The shape and geometry of the electrodes may vary however, it is preferable that the edges and corners of the electrodes are rounded, e.g. having a radius in range of about 0.15 mm to 2.5 mm, to “soften” the peaks of the electric field at the edges and corners.

As shown in Figure 8D, it is possible to make an interdigitated electrode arrangement for one- side flat aerosol-forming substrate 110. However, dielectric heating may be improved by providing a second electrode arrangement identical to the electrode arrangement shown in Figure 8D on an opposite side of the aerosol-forming substrate 110. The electrodes of the second electrode arrangement can be configured to align with electrodes of the first electrode arrangement having an opposite polarity.

Alternatively, as shown in Figure 9, the interdigitated electrode arrangement may comprise a first and second electrode configured to interdigitate together around a cylindrical axis to form a tubular structure. In this embodiment, there are two pairs of three digits of the electrodes. Preferably, the tubular structure can have a diameter between 5 mm to 9 mm. The tangential distance between the electrodes of opposite polarity can be between 0.5 mm to 3 mm, preferably between 0.7 mm to 2.2 mm. Figure 10 illustrates an embodiment in which the distance between electrodes of opposite polarity varies across different regions of the electrode arrangement. This may be advantageous to modify the strength of the electric field in different regions of the electrode arrangement, thereby modifying the heating power delivered to different regions of an aerosol-forming substrate 110 heated using the electrode arrangement, to provide for sectional, zoned or partial heating.

Figures 11A-B show isometric and schematic illustrations of tubular interdigitated electrode arrangements for use in the oscillation circuit of Figures 2 and 3 configured to dielectrically heat an aerosol-forming substrate 110 positioned in a central cavity formed by the electrode arrangement. The electrode arrangement in Figures 11A-B comprises a series of axially aligned electrode bands positioned adjacent to electrode bands having opposing polarities. In such embodiments, the aerosol-forming substrate 110 is not positioned directly between opposing electrodes, but is still heated by the presence of the alternating electric field in its proximity. Stronger and more uniform heating of the aerosol-forming substrate 110 may be achieved using the electrode arrangement shown in Figure 11 B, which is configured such that electrical field between opposing polarity electrodes is strongest across the aerosol-forming substrate 110. Figures 11C-D illustrate how the plurality of electrode portions from the electrode arrangements of Figure 11A-B may be electrically connected to achieve an interdigitated configuration.

Figure 12 is a schematic illustration of an electrode arrangement formed on a low dielectric flexible carrier material, according to embodiments of the disclosure. The arrangement comprises first and second electrodes E1 , E2 formed on a flexible low dielectric carrier material 1145. Flexible low dielectric carrier material 1145 may comprise a polyimide, or other flexible, electrically insulating, high-temperature, and low dielectric material. In some embodiments, the flexible low dielectric carrier material 1145 comprises a polyimide having a dielectric constant below 3.0, which may be produced by either changing its structure to lower the dielectric constant, or with use of low-dielectric fillers. For example, the intrinsic structure of the polyimide may be modified using one or more of fluorine- containing groups, non-planar large conjugated structures, alicyclic structures, or adding low- dielectric fillers such as fluorinated graphene, mica.

While the embodiment of Figure 12 shows an interdigitated electrode arrangement similar to those described above, other electrode arrangements may also be used. Furthermore, the first and second electrodes Ei, E2 do not need to be provided on the flexible low dielectric carrier material 1145 in a specific position, orientation, or with any fixed separation distance from each other. In some embodiments, the first and second electrodes E1 , E2 are provided on the flexible low dielectric carrier material 1145 in a first position in which the first and second electrodes E1, E2 are not in alignment, then the flexible low dielectric carrier material 1145 is bent or rolled to move the first and second electrodes E1, E2 to a second position in which they are aligned. Although not shown in Figure 12, the flexible low dielectric carrier material 1145 may further comprise a first inductor Li and/or a second inductor L2. The low dielectric flexible carrier material 1145 further comprises a temperature sensor 1950 configured to detect a temperature of an aerosol-forming substrate positioned between the first and second electrodes Ei, E2. For example, the temperature sensor can be embedded into the carrier material 1145, or be placed on a surface thereof. A signal indicative of the detected temperature is received by the microcontroller 1880. Based on the detected temperature, the microcontroller 1880 or another microprocessor may control the heating operation of the aerosol-generating device as will become more apparent from Figures 15 and 16 below.

In some embodiments, the low dielectric flexible carrier material 1145 described above may comprise additional components or sections of the oscillation circuits described above, including a switching unit transistor T, and other passive components such as capacitors Ci , C2, the delay line DL, and sensors (optical, magnetic-field, electric-field). In this respect, most or all components of the oscillation circuit could be placed onto the same low dielectric flexible carrier material 1145, including switching transistor, resonant circuit, and capacitive element, for example as surface-mounted elements, for high volume manufacturing and testing.

In some embodiments, the temperature sensor 1950 may comprise a sensor which either penetrates or is physically coupled to the surface of the removable and insertable aerosol-forming substrate, as illustrated in Figure 12.

Another way to capture a value indicative of the temperature of the aerosol-forming substrate 110 is by measuring the temperature of the insulation/substrate material on which the electrode arrangement is placed.

For example, as discussed above, the carrier material for mounting the opposing electrodes E1, E2 can be polyimide or PEEK or another high-temperature plastic material, and the electrodes can be embedded or placed on a surface of such carrier material. While the dielectric constant (or relative permittivity) of such material could be lower than the aerosol-forming substrate 110, it is still dielectric and therefore will heat up, following a heating curve that is substantially proportional to the heating curve of the aerosol-forming substrate. This enables the temperature sensing system to determine a value indicative of the aerosol-forming substrate temperature based on a measured temperature of the carrier material on which the load capacitor CL is placed. This may be measured using a semiconductor temperature sensor directly placed onto the carrier material, and with wiring (or other communicative coupling) that leads to a control ler/microprocessor 1880.

Referring now to the embodiment of Figure 12, a temperature of the carrier material can be measured at an area between two electrodes E1 , E2 of opposite polarity, with a temperature sensor 1950 placed on a carrier material that is used to mount both electrodes E1 , E2. In some embodiments, a separate element is provided having a dielectric value that is similar to that of the aerosol-forming substrate 110, with a temperature sensor in measuring contact to measure a value indicative of the aerosol-forming substrate temperature. Also, the temperature value measured from the carrier material or film can be calibrated based on an algorithm, formula, look-up table, mapping calibration, regression analysis, correspondence table, trained artificial intelligence network, to approximate the actual temperature value of the substrate material by calculation. This is because with an increased depletion level of the aerosol-forming article, the dielectric constant (relative permittivity) of the substrate will decrease, while the dielectric constant of the carrier material will remain substantially unchanged. This calculation can be based on a revolving time of the heating session, and be based on a power consumption of the heater, e.g. for example by measuring the current, measured air temperature of the heating cavity.

In this respect, as described herein, there are different ways to not directly measure the actual temperature of the substrate 110, and to measure one or more other values, at least one of them being a temperature measurement of another area or location of the aerosol-forming device, for example but not limited to the temperature of the dielectric carrier film that is exposed to the electric field, the temperature of the air in the heating cavity, the temperature of the electrodes Ei and/or E2, the temperature of the electronic circuits of the aerosol-generating device, the temperature inside the housing of the aerosol-generating device, to thereafter determine a value indicative of the temperature of the substrate 110 with high accuracy. This allows to use a temperature sensing unit that may already be present, and may be easier to implement than a temperature sensing unit that is configured to directly measure the temperature of the removable aerosol-forming article.

Thus, a value indicative of the temperature of the dielectric substrate material is captured by measuring the temperature of the material of the carrier substrate or film where the electrodes are placed on. For example, the insulating and/or carrier material for the opposing electrodes can be polyimide or PEEK or other high-temperature plastic material, and the electrodes can be embedded or placed on a surface of such insulating material. While the dielectric constant or relative permittivity of such material could be lower than the substrate material, it is still dielectric (2.8 to 4.0) and therefore will heat up, for example following a heating curve that is substantially proportional to the heating curve of the substrate. This allows to measure a value indicative of the substrate temperature by measuring a temperature of the insulation/carrier material of the electrodes of the load capacitor CL, for example by a semiconductor temperature sensor directly placed onto the insulator/carrier material, and with wiring that leads to a controller/microprocessor. As a non-limiting example, taking the interdigitated electrodes E1, E2, a temperature of the insulator/carrier material can be measured at an area between two electrodes of opposite polarity, with a temperature sensor placed on a common insulator/carrier that is used for both electrodes E1 , E2. It is also possible that a separate element is provided that has a dielectric value that is similar to the one of the aerosol-forming substrate S, with a temperature sensor in measuring contact therewith, to measure a value indicative of the substrate temperature S.

The temperature sensor is configured to measure temperatures in the region of 80°C-365°C, preferably 180°C-320°C, more preferably 180°C-220°C, more preferably 80-300°C, and may comprise one or more of thermocouples, thermistors, resistance-based temperature detectors (RTDs, PT100), thermoelements, fiber-optic temperature sensors. In some embodiments, the temperature sensor comprises one or more non-contact sensors such as an NIR sensor.

It should be noted that a direct temperature measurement of the substrate 110 may be difficult, as the aerosol forming substrate is removable, and due to the dielectric heating principle that heats any dielectric material in the alternating electric field. Therefore, the system may actually not measure the substrate temperature, but uses different measurements (at least one of them being a temperature measurement) and thereby calculates a value indicative of the substrate temperature (by algorithm, formula, look-up table, correspondence table, mapping, calibration, regression analysis, trained Al network). One of the factors to take into account is the time that has revolved of the heating session (e.g. we have heated for 30 seconds, so the temperature should be about in this or that range).

A direct temperature measurement of the substrate temperature is possible, when the temperature sensor is of non-contact type (NIR sensor) and is placed at an opening, hole, or cut-out section that is located inside an electrode E1 or E2. In this respect, the temperature sensor is not between the electrodes of opposite polarity, but in the middle or inside one. This could be useful for measurement temperatures of flat, planar, or card-like aerosol-forming substrates. In some embodiments, the temperature sensing system may be configured to measure a temperature of the electrodes or of the air inside the cavity, however, since these are not dielectric they will heat-up following a different temperature profile based on heat transfer from the aerosol-forming substrate. A controller may receive a measured temperature of the electrodes or the air around the aerosolforming substrate and calculate or deduce a value indicative of the substrate temperature, for example using one or more of a formula, look-up table, and or artificial intelligence network training.

Instead of or in addition to temperature sensors, which output a signal indicative of the temperature over a larger range of temperature, also one or more temperature markers may be employed. A temperature marker signifies herein a sensing element which changes a physical state when transitioning past a defined marker temperature. The change in physical state is then transduced into an electrical output signal.

A first example of a temperature marker comprises a susceptor material with a particular Curie temperature. The Curie temperature may be between about 200°C and about 450°C, preferably between about 240°C and about 400°C, for example about 280°C. As a general rule, whenever a value is mentioned throughout this application, this is to be understood such that the value is explicitly disclosed. However, a value is also to be understood as not having to be exactly the particular value due to technical considerations.

The published International applications WO2015/177294 A1 , WO2018/041924 A1 , W02020/064686 A1 describe the use of magnetic temperature markers having a Curie temperature to change the magnetic characteristics at a given temperature. The contents of the above three applications are all incorporated by reference as if fully set forth herein in their entirety. Once the susceptor material has reached its Curie temperature, its magnetic properties change. At the Curie temperature the susceptor material reversibly changes from a ferromagnetic phase to a paramagnetic phase. By inductively energizing the susceptor by means of an inductor coil this phase-change of the susceptor material may be detected. The control unit can be in operative connection with a measurement coil that can be configured to magnetize the temperature markers, and a change in impedance can be measured that is indicative of the reaching of a certain temperature.

For example a control unit, associated to a power supply of a device and the measurement, may be capable of detecting when the susceptor material has reached its Curie temperature by monitoring the values of the current absorbed by the inductor.

Also a dielectric temperature marker can be used according to the present disclosure. As is generally known, the dielectric constant of a polar material changes over temperature not continuously, but with stepwise discontinuities. The temperature of the discontinuities is dependent on the polar material and can be used as a marker temperature by detecting the abrupt change of the dielectric constant. There are several discontinuities in the dielectric constant as temperature changes. For instance, the dielectric constant changes abruptly at phase boundaries of the polar material.

As a specific example, water content can be used as a marker to detect an exact moment when a threshold temperature of 100°C is reached.

According to a further example, one type of temperature marker can mark a lower temperature of a desired range, and one other type of temperature marker could mark a higher temperature of the same range. Thus, it is possible to detect when the reference temperature of the marker is exceeded or otherwise breached. For example, a material having dielectric temperature marker properties can be embedded into the aerosol forming substrate, or in the aerosol-forming material, or could be part of the heating cavity, for example one or more layers of material that is embedded into the carrier film, and is exposed to the alternating electric field. One such material is PET etc. etc.

Another way of physically implementing the electrode arrangements described above is to use quartz glass (either fused quartz or fused Silica) as a substrate material, and to place electrodes on a surface of a quartz glass using a deposition process. Figure 13 is a schematic illustration of an electrode arrangement and two inductively coupled inductors Li, L2 formed on a quartz glass substrate 1345, according to embodiments of the disclosure.

In the illustrated embodiment, a first and second electrode 1330, 1335 is arranged on an outer surface of a cylindrical quartz glass substrate 1345 with the inner cylindrical volume defining a cavity 1340 for receiving an article 1305 comprising an aerosol-forming substrate 1310. Similar to the embodiments described above with respect to Figure 16, first and second inductors Li, L2 are positioned on opposite sides of the quartz glass substrate 1345, with a magnetic core Me extending through the center of the first and second inductors Li, L2, strengthening the mutual inductive coupling between them.

In an alternative embodiment, the first and second electrodes 1330, 1335 may be positioned on an inner surface of two opposing quartz glass surfaces, where an aerosol-forming substrate 1310 may be inserted therebetween.

In the embodiment of Figure 13, cavity 1340 is formed with the quartz glass substrate 1345, which serves as a transparent protective layer for an optical measurement device 1350 (for example optocouplers) for measuring aerosol diffusion for puff detection, temperature sensors for measuring thermal radiation, and time-of-f light sensors for measuring stick presence and other properties. Optical measurement device 1350 may comprise an optical emitter or light source 1354, an optical receiver or photo-sensitive device 1353, and the walls of the quartz glass substrate 1345 can include optical channels with a different refractive index than the quartz glass to act as waveguides or lightguides 1351 and 1352. Waveguides 1351 and 1352 may be embedded into the quartz glass substrate 1345, for example as channels, conduits, or holes, and can be filled with a transparent material having a different refractive index to the quartz glass substrate 1345. The light guides 1351 and 1352 can be used to guide light towards and away from cavity 1340 for illumination or measurement purposes.

Quartz glass provides for optical transmission into the ultraviolet and infrared spectrum, and advantageously exhibits low thermal expansion so is able to endure repeated heating cycles without damage or degradation. The smooth surfaces achievable with quartz glass provide a cavity 1340 with cleanable surfaces that can also reduce the accumulation of contaminants. In addition, quartz glass has good thermal insulation properties that allows to provide heat insulation around the cavity 1340, for concentrating the heat within the aerosol-forming substrate 1310.

Advantageously quartz glass has a lower dielectric constant (also referred to as the relative permittivity) than other glass materials, reducing the extent of parasitic heating from the dielectric heating circuit and generated electric field.

Quartz glass can also be machined or otherwise processed to form different shapes and arrangements. This allows to integrate other aspects with the electrode arrangement that is formed by the glass structure, including ribs, grooves, and channels for optimizing airflow through the aerosol-generating device. In some embodiments, the upstream air intake comes from ribs and grooves that are arranged to be in parallel with a rotational axis of a heating chamber comprising the electrode arrangement. In such embodiments, it is possible to provide for a heating chamber that is defined by glass walls, allowing for external sensing of parameters (temperature, airflow, puffs, etc.) with optical means for example optical measurement device 1350, permitting easy cleaning and reduced deposition of contaminants to the inner surfaces, and also allows the integration of inductive cores and windings of inductors. Figure 14 is a schematic illustration of a further temperature sensing system for detecting a temperature of an aerosol-forming substrate 110 situated with the electrode arrangement, according to embodiments of the disclosure. The system comprises a heat sensor 1850 communicatively coupled to a controller 1880. The heat sensor 1850 is configured to detect in a non-contact manner a temperature of an aerosol-forming substrate 110 situated between electrodes of an electrode arrangement and subject to dielectric heating as described above.

In an embodiment, the aerosol-forming substrate temperature is measured or approximated by the temperature sensing system. The measured or approximated temperature value may be fed to a temperature control loop unit configured for controlling power supplied to the aerosol-forming substrate.

As illustrated in Figure 14, one way to measure the temperature is by using a non-contact sensor (such as a near infrared sensor (NIR)), to capture heat radiation from the aerosol-forming substrate 110, or from a plate/device 1890 at the aerosol-forming substrate 110 material that increases or homogenizes the heat radiation and has greater thermal conductive properties than the aerosol-forming substrate 110.

Figure 15 is a schematic illustration of a control system utilizing a temperature sensing system for controlling the power delivered to an aerosol-forming substrate 110 based on a detected aerosol-forming substrate temperature. The control system comprises a controller configured to receive aerosol-forming substrate temperature data from a temperature sensing device, as described above. Where the controller determines that the aerosol-forming substrate temperature exceeds a predetermined upper threshold, the controller cuts the power to an oscillation circuit using a DC/DC cut off so that a fixed and variable temperature may be delivered to the aerosol-forming substrate.

In an alternative embodiment, the controller may be configured to use pulse width modulation (PWM) to vary the on and off duty ratio of an on-time (during which the oscillation circuit is running and heating) and an off-time (during which the oscillation circuit is not running and therefore not heating) of the oscillation circuit based on a measured or estimated temperature. In words, nothing of the oscillation is changed, just a different on-time versus off-time ratio is used to control the temperature in a closed loop manner

As an alternative to cutting the power supply from the oscillation circuit, the biasing voltage of the switching unit can be manipulated to put the transistor outside of a range where oscillation occurs. Either the biasing or DC voltage, or the DC supply voltage could be increased or lowered, to increase or lower the heating power delivered to the load capacitor CL until a measured temperature of the aerosol-forming substrate reaches a target temperature or is within a target temperature range.

In an alternative embodiment, the feedback loop of the oscillation circuit may be disrupted, for example by electrical or mechanical means. In some embodiments, the control system is configured to control the power delivered to the aerosol-forming substrate in two stages; a first stage where the aerosol-forming substrate temperature is ramped up as fast as possible and the heating power delivered to the substrate is maximized for fast heat up (also referred to as the preheating phase), and a second stage where the aerosol-forming substrate is maintained at a target aerosolization temperature.

The first stage is performed by maximizing the DC supply voltage to, for example 10V to 12V. Once the target aerosolization temperature is reached, for example in a range in between 80°C to 365°C, preferably 180°C to 320°C, more preferably 180°C to 220°C, the heating power is decreased by reducing the supply voltage to a lower value, for example around 6.4V to 7.6V. During the ramp- up time of the first stage of the temperature control, the overall power consumption can be 10W- 15W, preferably with an efficiency of at least 65%. During this first heat-up or preheating stage, a heating power per volume of substrate material delivered can be in a range between 10W/cm³ and 30W/cm³ and upon reaching aerosolization temperature of the aerosol former, the temperature can be controlled to 150°-220°, for example to achieve constant aerosol delivery for a given session duration. During the second stage, the heating power per volume of substrate material be in a dropped to be in range between 2W/cm³ to 10W/cm³.

Upon aerosolization of portions of the aerosol-forming material of the aerosol-forming substrate, there will typically be a change in DC supply current, as the dielectric constant of the aerosol-forming substrate will drop with increased depletion. The dielectric constant can therefore be used as a value that is indicative of the temperature of the aerosol-forming substrate.

In some embodiments, an artificial intelligence network is used to determine the temperature of the aerosol-forming substrate based on one or more of the heating cavity temperatures, the DC supply voltage, or the DC supply current. The artificial intelligence networked may have been trained with a training data set from different heated substrate materials under various conditions, including but not limited to various environmental temperatures, session durations, number of puffs, different environmental humidity, different stick humidity.

Figure 16 illustrates a more detailed block diagram of the control system for closed-loop temperature control utilizing a temperature sensing system for controlling the power delivered to an aerosol-forming substrate 110 based on a detection or measurement of a value that is indicative of the temperature of the aerosol-forming substrate 110. In particular, this Figure shows the selfoscillating circuit 250 of Figure 3A in an exemplary application environment. A power supply 2020 powers the oscillating circuit 250 via the DC-DC converter 2010 to be able to provide a variable DC supply voltage level to the oscillation circuit 250, and is in particular connected to the switching unit 260 to provide for the DC supply voltage via a DC/DC converter 2010. A microprocessor 2030 receives a signal indicative of the temperature of the substrate from the resonant circuit 272 where the load capacitor CL and the to-be-heated substrate 110 is located. The microprocessor 2030 may further receive a signal indicative of the power, current, and/or voltage provided by the DC/DC converter 2010 to the switching nit 260. The microprocessor 2030 can further have access to additional data and measurements that allows to calibrate the value that is indicated of the temperature of the substrate 110, for example a revolving time of the heating session, a temperature of the electronic circuit, a temperature of the air of the heating cavity, and the signal indicative of the power consumption, and can calibrate the temperature value to closely match an effective temperature of the substrate S, and can output a control signal to the DC/DC converter 2010 for controlling a voltage level that can be delivered as an input DC voltage to the self-oscillating circuit 260, for closed loop temperature control.

As an alternative to cutting the power supply from the dielectric heater circuit, also the biasing voltage could be moved to put the switching unit 260 outside of a range where oscillation happens with the biasing or DC voltage, or the DC supply voltage could be increased or lowered, to thereby increase or lower the heating power at the load capacitor CL to control the temperature based on a measured value, in comparison to a desired set value.

As another alternative, it is possible to disable the resonant feedback loop FL, for example by electrical or mechanical means. For example, the circuit could be mechanically disrupted by a switch, magnetized to move one or more inductors to saturation, etc.

In terms of a temperature profile, one could control the power delivered to the substrate S in two stages. A first stage is a stage where the substrate temperature is ramped up as fast as possible. This stage may also be called a pre-heating phase. Then, a second stage follows at which the delivered power is reduced. This phase may be referred to as a puff heating phase.

This can be done by maximizing the DC supply voltage. For instance, for the specific selfresonating circuit shown in Figure 16, the only way to decrease the temperature ramp-up or preheating time (by increasing the heating power once the circuit is on and running) is to increase the DC supply voltage to a maximal desired value, e. g. between 10V to 12V, and once the aerosolization temperature is reached, for example in a range between 150°C and 250°C, more preferably 150°C and 220°C, the heating power is decreased for reducing the supply voltage to a lower value, for example around 6.4V to 7.6V (e. g. double the nominal cell voltage of each of two lithium-ion battery cells put in series). For an exact timing when to switch from upper DC supply voltage level to the lower level, it is advantageous have accurate feedback on the temperature of the substrate by measurement.

In other words, during the pre-heating phase at least 70% of a maximum supply voltage of the power source, preferably more than 80% of the maximum supply voltage of the power source are supplied to the oscillation circuit. Then, during the puff heating phase, between 40% and 60% of a maximum supply voltage of the power source, preferably around 50% of the maximum supply voltage of the power source is supplied to the oscillation circuit as a reduced power.

However, upon aerosolization of the Glycerol-based aerosol-former, one could expect to see a change in DC supply current, as the dielectric constant or relative permittivity will drop. This can also be used as a value that is indicate of the temperature. As indicated above, one could use various ways to determine the substrate temperature by calculation, for example but not limited to an algorithm, formula, look-up table, correspondence table, mapping, calibration, regression analysis, trained Al network or model to determine the temperature of the substrate itself based on a heating cavity temperature, power DC supply voltage, DC supply current, revolving time of the heating session.

During the ramp-up or preheating time, the overall power consumption can be 10W-15W, preferably with an efficiency of at least 65%, and upon reaching aerosolization temperature of the aerosol former, the temperature can be controlled to 200°-220°, for example, to achieve constant aerosol delivery for a given session duration.

Furthermore, it is common that the substrate includes a certain percentage of water, for example caused from environmental humidity. Water is known to have a high dielectric value (about 80). The water content therefore will most likely increase the overall dielectric constant of the aerosolforming substrate, as the other material will have a lower dielectric constant. When starting a heating session, during the heating ramp-up or preheating phase, one can therefore observe a DC feeding current that increases until the vaporization temperature of water has been reached (about 100°C). Thereafter, due to the removal of water, the DC feeding current will drop again until the aerosolization temperature is reached (about 200°C). The presence of water will therefore have an impact on the capacitance value of CL, and will most likely slow down the switching frequency fs. This leads to a reduction of the possible heating power. To compensate for this effect, one can maximize the DC feed voltage to the start-up phase. Preferably, during the first heat-up or preheating stage, a heating power per volume of substrate material delivered can be in a range between 10W/cm³ and 30W/cm³, and during the second stage, the heating power per volume of substrate material be in a dropped to be in range between 2W/cm³ to 10W/cm³. Generally, the oscillation circuit 150, 250 can be configured to provide at least 1W/cm² of heating power to the aerosol-forming substrate 110.

It will be appreciated that many of the embodiments described above do not rely on the use of a self-oscillating oscillation circuit, and can therefore be implemented using a forced oscillation circuit such as that illustrated in Figure 17, while still providing the described function and advantages. Specifically, an oscillation unit may be coupled to a switching unit, amplification unit, or buffer to convert a DC supply voltage to an AC signal fed to a resonant or quasi-resonant circuit comprising the load capacitor.

In an embodiment, the oscillation unit and switching unit circuitry comprises one of a single transistor, half-bridge or full-bridge architecture. In such embodiments, zero current switching techniques may be used to reduce or minimize switching losses, using a parallel or series resonant circuit or tank circuit. In an embodiment, the oscillation unit is implemented as a stripline oscillator.

The heating and depletion of the aerosol-forming substrate leads to a change in the resonant frequency due to decrease of the dielectric constant and hence of the capacitance [Farad] of the capacitor, as the load capacitor CL is part of the resonant circuit 272 that can be self-oscillating at or close to a resonance frequency.

In one embodiment, a frequency sensor is used to correlate different power consumption patterns (e.g. DC current that is fed from the power source by power analysis) with the frequency of oscillation for a particular oscillation circuit and aerosol-forming substrate type. A control system can then use a power consumption value (DC supply current, voltage, both) as a parameter that is indicative of a depletion of a substrate.

Figure 18 is a schematic illustration of a control system utilizing a frequency sensing system for controlling the power delivered to an aerosol-forming substrate based on a frequency of an alternating electric field detected across an electrode assembly, according to embodiments of the disclosure. In an exemplary variant, the system comprises a electric field probe that includes a resonant cavity (e.g., quarter wavelength) having a peak resonant frequency above the switching frequency of the oscillating feedback loop, for example the resonant frequency of the feedback loop 270, or a frequency close to it due to the effect of a delay line DL. The resonant cavity is prepared, for example, by the use of impurities or mechanical imperfections, to have a spread-out frequency response showing a variation between the different frequencies, such that the operational range of frequencies is covered by a resonant response. In one embodiment, a coaxial cavity resonator for quarter wave with an inner wire is used, having an impurity-doped insulator.

The resonant cavity is interfaced with a direct electric coupler to a rectifier to generate a DC signal, which is applied to a resistor/impedance to be measured by a voltage sensor, and fed to a controller/microprocessor for calibration/further processing.

The resonant cavity is placed into the electric field that is generated by the load capacitor CL, for example at a peripheral area thereof, or a special area of the heating cavity could be arranged such that only the measurement probe would be placed there, and would not obstruct the aerosolforming substrate.

In an alternative embodiment, the electric field probe may utilize one or more of resonant antennas, microstrips, waveguides, for high-frequency sensing.

It will be appreciated that the embodiments described above are exemplary embodiments only, and various other embodiments according with this disclosure are also envisaged.

For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term “about”. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein. In this context, therefore, a number A is understood as A ± 5% of A.

Claims

CLAIMS:

1. An aerosol-generating device for dielectrically heating an aerosol-forming substrate, the aerosol-generating device comprising: a power source; an oscillation circuit including a resonant feedback circuit and a switching unit powered by the power source forming a self-oscillating circuit; a dielectric heating element fed by the oscillation circuit, the dielectric heating element being a capacitor for the resonant feedback circuit, the dielectric heating element being arranged for heating the aerosol-forming substrate by dipole rotation when subjected to an alternating electric field caused by the dielectric heating element; a temperature determining unit for measuring a value indicative of a temperature of the aerosol-forming substrate; and a controller for controlling the temperature of the aerosol-forming substrate by changing a parameter or configuration of the aerosol-generating device based on a signal from the temperature determining unit.

2. The aerosol-generating device according to claim 1 , wherein the oscillation circuit comprises a resonant feedback circuit including the dielectric heating element, so that the oscillation circuit is self-resonating.

3. The aerosol-generating device according to claim 1 , wherein the temperature determining unit comprises at least one of a temperature sensor, a temperature probe, and a temperature marker.

4. The aerosol-generating device according to claim 1 , wherein the oscillation circuit comprises an oscillation unit for controlling the switching unit with a defined switching frequency, wherein the oscillation unit comprises a DC-to-AC converter, a stripline oscillator, or an oscillation circuit with an amplifier or buffer.

5. The aerosol-generating device according to any of the preceding claims, wherein the change of the parameter or configuration of the aerosol-generating device includes at least one of: enabling or disabling the switching unit by respectively establishing or disabling an electrical connection between the power source and the switching unit; enabling or disabling the switching unit by using a biasing circuit to respectively enable or disable a switching of a transistor of the switching unit by moving the switching unit into an inoperable range of voltage or current; enabling or disabling the switching unit by respectively enabling or disabling the resonant feedback circuit; and changing a switching frequency of the switching unit.

6. The aerosol-generating device according to any of the preceding claims, wherein the change of the parameter or configuration of the aerosol-generating device includes controlling by the controller a level of the DC supply voltage provided by the power source based on a signal from the temperature determining unit, and further comprising a voltage controlling unit electrically interconnected with the power source, configured to provide the DC supply voltage with a time-variable level, wherein the voltage controlling unit includes a DC-DC converter, preferably a boost, buck, half-bridge, or full bridge converter, a voltage regulator, a charge pump circuit, or a combination thereof, and wherein the DC supply voltage is provided as the output voltage of a voltage regulator or of a DC-DC converter.

7. The aerosol-generating device according to any of the preceding claims, wherein at least one of: the change of the parameter or configuration of the aerosol-generating device is performed so that the oscillation circuit is enabled when the temperature of the aerosol-forming substrate is below or at a first threshold value, and the oscillation circuit is disabled when the temperature of the aerosol-forming substrate is above or at a second threshold value; the change of the parameter or configuration of the aerosol-generating device is performed by controlling the heating of the aerosol-forming substrate in a pulse width modulation, PWM, operation, wherein a ratio of a heating time duration to a non-heating time duration is changed based on a signal from the temperature determining unit by respectively enabling and disabling the oscillation circuit; and the signal from the temperature determining unit is compared to a defined set value, and wherein the change of the parameter or configuration of the aerosol-generating device is performed in response to a result of the comparison, so that a closed loop temperature control is performed.

8. The aerosol-generating device according to any of the preceding claims, wherein the controller is operable to control the temperature of the aerosol-forming substrate by first applying a preheating phase to reach a first target temperature at which at least one component of the aerosol-forming substrate vaporizes or at which a maintenance heat level is reached.

9. The aerosol-generating device according to claim 8, wherein at least one of: the controller is operable to control the temperature of the aerosol-forming substrate to perform, after performing the preheating phase, a puff heating phase where the temperature is maintained at least at a second target temperature; and the controller is operable to provide a first heating power during the preheating phase, the first heating power being higher than a second heating power provided during the puff heating phase.

10. The aerosol-generating device according to any of the preceding claims, wherein the temperature determining unit includes a temperature sensor that is operable to capture a temperature of an element that is separate to the aerosol-forming substrate placed such that is exposed to the alternating electric field of the dielectric heating element, wherein the element is made of at least one material that has a dielectric constant that is similar to the aerosol-forming substrate.

11. The aerosol-generating device according to any of the preceding claims, at least one of: wherein the dielectric heating element comprises at least two electrodes that are placed on or inside a dielectric carrier film or material, and wherein the temperature determining unit is operable to capture the temperature of the dielectric carrier film or material; wherein the temperature determining unit is arranged on, at, or within a dielectric carrier film or material between two neighboring electrodes of opposite polarity; wherein the dielectric heating element comprises at least two electrically conductive electrodes and wherein the temperature determining unit is operable to capture a temperature of at least one of the electrodes, wherein the temperature determining unit comprises a thermistor, a resistance-based temperature detector, a thermocouple, a fiberoptic temperature sensor, or a thermopile; and wherein the temperature determining unit comprises a non-contact temperature sensor arranged for detecting a heat radiation indicative of the temperature of the aerosol-forming substrate, the temperature determining device comprising an infrared temperature sensor, an infrared camera, a pyrometer, a pyroelectric sensor, a time-of-flight sensor, or a combination thereof.

12. The aerosol-generating device according to claim 10 or 11 , wherein an aerosol-generating article comprising the aerosol-forming substrate includes a plate or surface exposed towards the temperature sensor when the aerosol forming substrate is operational connection with the dielectric heating element, the plate or surface having an increased thermal radiation emissivity compared to materials used for the aerosol-forming substrate.

13. The aerosol-generating device according to any of the preceding claims, at least one of: wherein the temperature determining unit comprises a temperature probe arranged for penetrating the aerosol-forming substrate, when the aerosol-forming substrate is arranged in operational connection with the dielectric heating element; wherein the temperature determining unit comprises an electric field probe or electric field sensor, the electric field probe or electric field sensor comprising a dielectric resonator or antenna for detecting an electric field at the aerosol-forming substrate, and the controller being operable to derive the temperature of the aerosol-forming substrate from the detected electric field; wherein the temperature determining unit is operable to determine the temperature of the aerosol-forming substrate based on at least one of a heating cavity temperature, a DC supply voltage, a DC supply current, and/or DC supply power, the controller comprising a trained artificial intelligence network for deriving the temperature of the aerosol-forming substrate based on measured values, the measured values including at least one of the heating cavity temperature, the DC supply voltage or current, power consumption, an electronic circuit temperature, and a revolving time value; and wherein the temperature determining unit comprises a current sensor for monitoring changes of a heating power, in particular a DC supply current, and wherein the controller is operable to derive the temperature of the aerosol-forming substrate from the detected changes in the heating power, in particular the DC supply current.

14. A method of dielectrically heating an aerosol-forming substrate by means of an aerosolgenerating device, the method comprising the following steps: dielectrically heating the aerosol-forming substrate by dipole rotation when subjected to an alternating electric field caused by a dielectric heating element, wherein the dielectric heating element is comprised in an oscillation circuit of the aerosol-generating device, the dielectric heating element being a capacitor for the resonant feedback circuit, the oscillation circuit including a resonant feedback circuit and a switching unit powered by a power source forming a self-oscillating circuit; measuring a value indicative of a temperature of the aerosol-forming substrate; and controlling the temperature of the aerosol-forming substrate by changing a parameter or configuration of the aerosol-generating device based on the measured value.

15. An aerosol-generating system comprising: an aerosol-generating article comprising an aerosol-forming substrate and an aerosol-generating device for dielectrically heating the aerosol-forming substrate, the aerosol-generating device comprising: a power source; an oscillation circuit including a resonant feedback circuit and a switching unit powered by the power source forming a self-oscillating circuit; a dielectric heating element fed by the oscillation circuit, the dielectric heating element being a capacitor for the resonant feedback circuit, the dielectric heating element being arranged for heating the aerosol-forming substrate by dipole rotation when subjected to an alternating electric field caused by the dielectric heating element; a temperature determining unit for measuring a value indicative of a temperature of the aerosol-forming substrate; and a controller for controlling the temperature of the aerosol-forming substrate by changing a parameter or configuration of the aerosol-generating device based on a signal from the temperature determining unit.

16. The aerosol-generating system according to claim 15, wherein at least one of: the aerosol-forming substrate comprises a solid material with an aerosol former; and the dielectric heating element is formed as a separate insertable and removable part of the aerosol-generating device.