WO2025185338A1 - Antenna structure and mobile terminal - Google Patents

Abstract

The present application provides an antenna structure and a mobile terminal. The antenna structure comprises a radiator and an impedance matching circuit. The radiator comprises a first branch and a second branch which are connected, an end of the first branch facing away from the second branch being an open end, the first branch comprising a feed point, an end of the second branch facing away from the first branch being grounded, and a connecting point of the first branch and the second branch being grounded by means of an inductive structure. A physical length L1 of the first branch and a physical length L2 of the second branch satisfy 4/5≤L1/L2≤4/3, and a distance d between the feed point and the end of the first branch facing away from the second branch satisfies d≤1/4×L1. The impedance matching circuit is electrically connected to the feed point, and the impedance matching circuit comprises an inductor. The present application, by means of constructing an antenna structure to be a same-direction slot antenna, so that electric fields generated by all parts of the radiator of the antenna structure are in the same direction, makes it convenient to tune the radiation pattern on a side of the antenna structure facing a display screen, so as to optimize handheld performance of the antenna structure.

Description

Antenna structure and mobile terminal

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of the People's Republic of China on March 4, 2024, with application number 202410259371.5 and application name "An antenna structure and mobile terminal", the entire contents of which are incorporated by reference into this application.

Technical Field

The present application relates to the field of communication technology, and in particular to an antenna structure and a mobile terminal.

Background Art

With the development of mobile communications, the usage rate of mobile terminals is increasing. The network coverage of mobile cellular networks is the key to mobile communications, and the key equipment used by mobile cellular networks to achieve network coverage is the antenna.

In current mobile terminals, the frame antenna used to radiate low-frequency signals is typically located on one side of the battery compartment. The length of the radiator is approximately one-quarter of the wavelength corresponding to the center frequency of the antenna's resonant frequency. This antenna has high radiation efficiency in free space. However, when the user is holding the mobile terminal, much of the energy radiated by the frame antenna toward the rear case is blocked by the hand. Consequently, the radiated energy of the frame antenna is significantly reduced, affecting its radiation performance.

Based on this, how to ensure the radiation efficiency of the antenna in free space while effectively reducing the reduction in the radiation energy of the antenna when the mobile terminal is in the handheld state has become a difficult problem that needs to be solved urgently by those skilled in the art.

Summary of the Invention

The present application provides an antenna structure and a mobile terminal, which optimize the hand-holding performance of the antenna structure while ensuring the radiation efficiency of the antenna structure in free space, thereby improving the communication performance of the mobile terminal.

In a first aspect, the present application provides an antenna structure comprising a radiator and an impedance matching circuit. The radiator comprises a first branch and a second branch connected to each other, the end of the first branch facing away from the second branch being an open end, the first branch comprising a feeding point, the end of the second branch facing away from the first branch being grounded, and the connection point between the first branch and the second branch being grounded via an inductive structure. Furthermore, the physical length L1 of the first branch and the physical length L2 of the second branch satisfy 4/5≤L1/L2≤4/3. Furthermore, the distance d between the feeding point and the end of the first branch facing away from the second branch satisfies d≤1/4×L1. Furthermore, the impedance matching circuit is electrically connected to the feeding point, and the impedance matching circuit comprises an inductor. In the present application, by constructing the antenna structure as a co-directional slot antenna, the electric fields generated by the various parts of the radiator of the antenna structure are made co-directional, thereby facilitating tuning of the antenna structure's directional pattern toward the display screen, thereby ensuring the antenna structure's radiation efficiency in free space while also optimizing the hand-holding performance of the antenna structure.

The antenna structure provided in the present application can be used to operate in a low-frequency band, wherein the low-frequency band includes at least one communication frequency band within 600 MHz-1 GHz.

Additionally, the inductor in the impedance matching circuit can be used to perform impedance matching on the antenna structure to adjust the resonant frequency generated by the antenna structure. In one possible implementation, the inductor in the impedance matching circuit has an inductance greater than or equal to 15 nH to meet the impedance matching requirements of the antenna structure and facilitate the antenna structure generating an antenna pattern similar to a slot antenna.

In one possible implementation of the present application, the antenna structure further includes a tuning circuit, one end of the tuning circuit being grounded, and the other end of the tuning circuit being electrically connected between the impedance matching circuit and the feed point. Furthermore, the tuning circuit includes at least one capacitor. The at least one capacitor of the tuning circuit can be used to perform frequency tuning. That is, when the corresponding capacitor is electrically connected between the impedance matching circuit and the feed point, the antenna structure can operate in the corresponding communication frequency band.

In the present application, the capacitance of at least one capacitor of the tuning circuit is less than or equal to 2 pF, which is beneficial for the antenna structure to generate an antenna pattern similar to a slot antenna.

In addition, when the tuning circuit includes multiple capacitors, the multiple capacitors are arranged in parallel. In this way, by electrically connecting different capacitors between the impedance matching circuit and the feeding point, the antenna structure can be switched to a communication frequency band within the low frequency band.

The antenna structure provided in the present application may further include a feeding circuit, wherein the impedance matching circuit is electrically connected between the feeding circuit and the feeding point. The feeding circuit can be used to feed or transmit radio frequency signals, thereby enabling the antenna structure to receive or transmit radio frequency signals.

In the second aspect, the present application also provides a mobile terminal. The mobile terminal includes a frame and the antenna structure of the first aspect, the frame is arranged around the outer circumference of the mobile terminal, and the radiator of the antenna structure is arranged on one side of the frame. Among them, the radiator of the antenna structure can be a conductive part on the frame, for example, it can be the conductive frame itself, or the radiator can be a conductor on a non-conductive frame. The antenna for the low-frequency band of the mobile terminal provided by the present application adopts the design method of the above-mentioned antenna structure, which can effectively improve the directional pattern of the antenna structure toward the side of the display screen, so as to ensure the radiation efficiency of the antenna structure in free space while optimizing the radiation performance of the antenna structure when the mobile terminal is in a hand-held state.

In one possible implementation of the present application, the mobile terminal further includes a middle frame, the middle frame being located within the area enclosed by the frame, wherein the end of the second branch facing away from the first branch is connected to the middle frame to achieve grounding of the second branch. Furthermore, the connection point between the first branch and the second branch is connected to the middle frame via an inductive structure, thereby achieving grounding of the connection point between the first branch and the second branch.

Since the antenna structure provided in the present application operates in a low-frequency band, the antenna structure is arranged near the bottom of the mobile terminal. The middle frame also includes a battery compartment, which is used to accommodate batteries, and the battery compartment is also arranged near the bottom of the mobile terminal. Then in a possible implementation of the present application, the radiator is located on the side of one side of the frame facing the battery compartment, and along the direction from the second branch to the first branch, the connection point between the first branch and the second branch is lower than the top of the battery compartment. This can help improve the utilization rate of the portion of the frame that is arranged opposite to the battery compartment, and help increase the physical length of the radiator, thereby helping to improve the aperture of the antenna structure.

This application does not limit the specific configuration of the inductive structure. For example, the inductive structure may include a grounding rib located between the battery compartment and the radiator. One end of the grounding rib is connected to the connection point between the first branch and the second branch, and the other end of the grounding rib is connected to the middle frame.

In one possible implementation of the present application, the grounding rib, the middle frame, and the frame may be integrally formed. This ensures the reliability of grounding the connection point between the first and second branches via the grounding rib, and also facilitates improved structural integration of the mobile terminal. Furthermore, it facilitates controlling the space occupied by the grounding rib, reserving sufficient space for the battery, thereby meeting battery capacity requirements.

In one possible implementation of the present application, the sensor structure can also be an independent structural component, with the sensor portion of the sensor structure connected to the connection point between the first branch and the second branch, and also connected to the middle frame. This can help improve the flexibility of the sensor structure.

In one possible implementation of the present application, there is a clear space between the radiator and the middle frame, which can ensure that the radiator has a good radiation environment, thereby improving the signal transmission quality and coverage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic structural diagram of a mobile terminal provided in an embodiment of the present application;

FIG2 is a schematic diagram of a configuration method of a frame antenna in a mobile terminal according to the prior art;

[Corrected 23.01.2025 in accordance with Article 91]
FIG3 is a current distribution diagram of the frame antenna shown in FIG2 ;

[Corrected 23.01.2025 in accordance with Article 91]
[REDACTED]

FIG4 is a schematic diagram of the structure of a mobile terminal provided in an embodiment of the present application;

[Corrected 23.01.2025 in accordance with Article 91]
FIG5 is a schematic diagram of current flow in the antenna structure shown in FIG4 ;

[Corrected 23.01.2025 in accordance with Article 91]
[REDACTED]

FIG6 is a schematic diagram of current amplitude distribution of the antenna structure shown in FIG4 ;

[Corrected 23.01.2025 in accordance with Article 91]
FIG7 is a schematic diagram of the electric field distribution of the antenna structure shown in FIG4 ;

[Corrected 23.01.2025 in accordance with Article 91]
[REDACTED]

FIG8 is a comparison diagram of the radiation efficiency in free space of the antenna structure provided by an embodiment of the present application and the existing frame antenna shown in FIG2 ;

FIG9 is a comparison diagram of the radiation efficiency of the antenna structure provided in an embodiment of the present application and the existing frame antenna shown in FIG2 in a hand-held state.

Figure markings: 010-mobile terminal; 011-cover plate; 012-display screen/module; 013-printed circuit board; 014-middle frame; 0141-battery compartment; 015-back cover; 016-frame; 0161-slit; 1-radiator; 101-feeding point; 1a-first branch; 1b-second branch; 2-impedance matching circuit; 201-inductor; 3-tuning circuit; 301-capacitor; 4-inductive structure; 401-grounding connecting bar.

DETAILED DESCRIPTION

In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be understood as being limited to the embodiments set forth herein. The same figure marks in the figures represent the same or similar structures, and thus their repeated description will be omitted. The words expressing position and direction described in the embodiments of the present application are all explained with reference to the accompanying drawings as examples, but changes can be made as needed, and the changes made are all included in the scope of protection of the present application. The drawings in the embodiments of the present application are only used to illustrate the relative position relationship and do not represent the true proportion.

It should be noted that the following description sets forth specific details to facilitate understanding of the present application. However, the present application can be implemented in a variety of other ways than those described herein, and those skilled in the art may make similar generalizations without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

The following explains the terms that may appear in the embodiments of the present application.

Radiator (or antenna branch): It is a device in the antenna used to receive/transmit electromagnetic waves. In some cases, "antenna" is understood in a narrow sense as a radiator, which converts the guided wave energy from the transmitter into radio waves, or converts radio waves into guided wave energy, which is used to radiate and receive radio waves. The modulated high-frequency current energy (or guided wave energy) generated by the transmitter is transmitted to the transmitting radiator via the feeder line, and is converted by the radiator into a certain polarized electromagnetic wave energy and radiated in the desired direction. The receiving radiator converts the electromagnetic wave energy of a certain polarization from a specific direction in space into modulated high-frequency current energy, which is transmitted to the receiver input via the feeder line.

The radiator (or antenna branch) may include a conductor with a specific shape and size, such as a wire or sheet, etc., and the present application does not limit the specific shape. In one embodiment, the linear radiator can be simply referred to as a wire antenna. In one embodiment, the linear radiator can be implemented by a conductive frame, and can also be called a frame antenna. In one embodiment, the linear radiator can be implemented by a bracket conductor, and can also be called a bracket antenna. In one embodiment, the wire diameter (for example, including thickness and width) of the linear radiator, or the radiator of the wire antenna is much smaller than the wavelength (for example, the wavelength of the medium) (for example, less than 1/16 of the wavelength), and the electrical length is comparable to the wavelength (for example, the wavelength of the medium) (for example, the electrical length is about 1/8 of the wavelength, or 1/8 to 1/4, or 1/4 to 1/2, or longer). The main forms of wire antennas are dipole antennas, half-wave oscillator antennas, monopole antennas, loop antennas, and inverted F antennas (IFA). For example, for a dipole antenna, each dipole antenna typically includes two radiating branches, each branch being fed by a feed portion from the feed end of the radiating branch. For example, an inverted-F antenna can be considered to be a monopole antenna with a ground path added. The inverted-F antenna has a feeding point and a grounding point, and is called an inverted-F antenna because its side view is an inverted-F shape. In one embodiment, the sheet radiator may include a microstrip antenna or a patch antenna, such as a planar inverted-F antenna (PIFA). In one embodiment, the sheet radiator may be implemented by a planar conductor (such as a conductive sheet or a conductive coating). In one embodiment, the sheet radiator may include a conductive sheet, such as a copper sheet. In one embodiment, the sheet radiator may include a conductive coating, such as a silver paste. The shape of the sheet radiator includes circular, rectangular, annular, etc., and this application does not limit the specific shape. The structure of a microstrip antenna generally consists of a dielectric substrate, a radiator, and a ground plane, wherein the dielectric substrate is disposed between the radiator and the ground plane.

The radiator (or antenna branch) may also include a slot or slot formed in a conductor, for example, a closed or semi-closed slot or slot formed in a grounded conductor surface. In one embodiment, a slotted or slotted radiator may be referred to as a slot antenna or slot antenna. In one embodiment, the radial dimension (e.g., including the width) of the slot or slot of the slot antenna/slot antenna is significantly smaller than the wavelength (e.g., the dielectric wavelength) (e.g., less than 1/16 of the wavelength), and the electrical length may be comparable to the wavelength (e.g., the dielectric wavelength) (e.g., the electrical length is approximately 1/8 of the wavelength, or 1/8 to 1/4, or 1/4 to 1/2, or longer). In one embodiment, a radiator with a closed slot or slot may be referred to as a closed slot antenna. In one embodiment, a radiator with a semi-closed slot or slot (e.g., a closed slot or slot with an additional opening) may be referred to as an open slot antenna. In some embodiments, the slot is elongated. In some embodiments, the slot is approximately half a wavelength (e.g., the dielectric wavelength). In some embodiments, the slot is approximately an integer multiple of the wavelength (e.g., one wavelength). In some embodiments, the slot can be fed with a transmission line spanning one or both sides, thereby exciting a radio frequency electromagnetic field in the slot and radiating electromagnetic waves into space. In one embodiment, the radiator of a slot antenna or slot antenna can be implemented as a conductive frame with both ends grounded, also known as a frame antenna. In this embodiment, the slot antenna or slot antenna can be considered to include a linear radiator spaced from the floor and grounded at both ends, thereby forming a closed or semi-enclosed slot or slot. In one embodiment, the radiator of a slot antenna or slot antenna can be implemented as a bracket conductor with both ends grounded, also known as a bracket antenna.

A matching circuit is a circuit used to adjust the radiation characteristics of an antenna. In one embodiment, the matching circuit is coupled between the feed circuit and the corresponding radiator. Typically, the matching circuit is coupled between the test socket and the radiator. In one embodiment, the matching circuit performs impedance matching and/or frequency tuning functions. Generally, it is considered part of the antenna.

The tuning circuit is a circuit associated with adjusting the resonant frequency of the antenna. In one embodiment, the tuning circuit is coupled between the radiator and the floor. In one embodiment, the tuning circuit is coupled between the feed circuit and the radiator. In one embodiment, the tuning circuit performs impedance matching and/or frequency tuning functions. It is generally considered to be part of the antenna.

In one embodiment, the matching circuit/tuning circuit may include a switch and/or an electronic component/device. The switch may be an electronic component/device for switching the coupling connection of the radiator. The switch in the matching circuit/tuning circuit may also be referred to as an antenna switch. In one embodiment, the matching circuit/tuning circuit may include a filtering circuit.

The grounding structure/feeding structure may include a connector, such as a metal spring. The radiator is coupled to the floor via the grounding structure, and the radiator is coupled to the feeding circuit via the feeding structure. In some embodiments, the feeding structure may include a transmission line/feeding line, and the grounding structure may include a grounding wire.

The feed line, also known as the transmission line, refers to the connection line between the antenna's transceiver and the radiator. The transmission line can directly transmit current waves or electromagnetic waves, depending on the frequency and form. The connection point on the radiator to the transmission line is usually called the feed point. Transmission lines include wire transmission lines, coaxial transmission lines, waveguides, or microstrip lines. Depending on the implementation form, the transmission line can include a bracket antenna body or a glass antenna body. Depending on the carrier, the transmission line can be implemented by liquid crystal polymer (LCP), flexible printed circuit (FPC), or printed circuit board (PCB).

Ground/floor: can generally refer to at least a portion of any grounding layer, or grounding plate, or grounding metal layer, etc. in a mobile terminal (such as a mobile phone), or at least a portion of any combination of any of the above grounding layers, or grounding plates, or grounding components, etc. "Ground/floor" can be used for grounding components in the mobile terminal, or in other words, can be used as a reference ground for components in the mobile terminal. Generally, large pieces/large blocks of metal layers in a mobile terminal can be used as "ground/floor". In one embodiment, the "ground/floor" can include any one or more of the following: the grounding layer of the circuit board of the mobile terminal, the grounding plate formed by the middle frame of the mobile terminal, the grounding metal layer formed by the metal film under the screen, the conductive grounding layer of the battery, the metal hinge of the foldable mobile terminal, the metal back cover of the mobile terminal (for example, when at least a portion of the back cover is metal), and conductive parts or metal parts electrically connected to the above grounding layer/grounding plate/metal layer. In one embodiment, the circuit board can be a printed circuit board (PCB), such as an 8-layer, 10-layer, or 12-to-14-layer board having 8, 10, 12, 13, or 14 layers of conductive material, or components separated and electrically insulated by dielectric or insulating layers such as fiberglass, polymers, etc. In one embodiment, the circuit board includes a dielectric substrate, a ground layer, and a routing layer, and the routing layer and the ground layer are electrically connected through vias. In one embodiment, components such as a display, a touch screen, input buttons, a transmitter, a processor, a memory, a battery, a charging circuit, a system on a chip (SoC), etc. can be mounted on or connected to the circuit board; or electrically connected to the routing layer and/or ground layer in the circuit board. For example, a radio frequency source is provided in the routing layer.

Any of the above-mentioned grounding layers, grounding plates, or grounding metal layers are made of a conductive material. In one embodiment, the conductive material can be any of the following: copper, aluminum, stainless steel, brass, and alloys thereof, copper foil on an insulating substrate, aluminum foil on an insulating substrate, gold foil on an insulating substrate, silver-plated copper, silver-plated copper foil on an insulating substrate, silver foil and tin-plated copper on an insulating substrate, cloth impregnated with graphite powder, a graphite-coated substrate, a copper-plated substrate, a brass-plated substrate, and an aluminum-plated substrate. Those skilled in the art will appreciate that the grounding layer/grounding plate/grounding metal layer can also be made of other conductive materials.

Grounding refers to coupling with the ground/floor surface through a grounding structure and/or grounding circuit. In one embodiment, grounding can be achieved through physical grounding, such as achieving physical grounding (or physical ground) at a specific location on the frame through a portion of the middle frame's structural components. In one embodiment, grounding can be achieved through device grounding, such as grounding through a series or parallel connection of a capacitor, inductor, or resistor (or device ground).

Resonant frequency: The resonant frequency is also called the resonance frequency. The resonant frequency can have a frequency range, that is, the frequency range in which resonance occurs. The resonant frequency can be a frequency range in which the return loss characteristic is less than -6dB. The strongest resonance point can be called the resonance point, and the frequency corresponding to the resonance point is the center frequency point frequency. The return loss characteristic of the center frequency can be less than -20dB. It should be understood that, unless otherwise specified, the antenna/radiator mentioned in this application produces a "first/second... resonance", where the first resonance should be the fundamental mode resonance generated by the antenna/radiator, or in other words, the lowest frequency resonance generated by the antenna/radiator. It should be understood that the antenna/radiator can generate one or more antenna modes according to the specific design, and each antenna mode can generate a corresponding fundamental mode resonance.

Resonant frequency band: The range of the resonant frequency is the resonant frequency band, and the return loss characteristic of any frequency point in the resonant frequency band can be less than -4dB.

Communication frequency band/operating frequency band: Regardless of the type of antenna, it always operates within a certain frequency range (bandwidth). For example, an antenna that supports the B40 frequency band has an operating frequency band of 2300MHz to 2400MHz, or in other words, the antenna's operating frequency band includes the B40 frequency band.

The resonant frequency band and the operating frequency band may be the same, or may partially overlap. In one embodiment, one or more resonant frequency bands of the antenna may overlap one or more operating frequency bands of the antenna.

Electrical length: Electrical length can be expressed as the ratio of the physical length (i.e., mechanical length or geometric length) multiplied by the transmission time of an electrical or electromagnetic signal in a medium to the time required for the signal to travel the same distance as the physical length of the medium in free space. The electrical length can satisfy the following formula:

Where L is the physical length, a is the propagation time of the electrical or electromagnetic signal in the medium, and b is the propagation time in free space.

Alternatively, electrical length can also refer to the ratio of physical length (i.e., mechanical length or geometric length) to the wavelength of the transmitted electromagnetic wave. The electrical length can satisfy the following formula:

Where L is the physical length and λ is the wavelength of the electromagnetic wave.

In some embodiments of the present application, the physical length of the radiator may be understood to fall within a range of ±20%, or within a range of ±10%, or within a range of ±5% of the electrical length of the radiator.

Wavelength: Or operating wavelength, this can be the wavelength corresponding to the center frequency of the resonant frequency or the center frequency of the operating frequency band supported by the antenna. For example, if the center frequency of the B1 uplink frequency band (resonant frequency 1920MHz to 1980MHz) is 1955MHz, the operating wavelength can be the wavelength calculated using 1955MHz. "Operating wavelength" is not limited to the center frequency; it can also refer to the wavelength corresponding to a non-center frequency of the resonant frequency or operating frequency band.

It should be understood that the wavelength of the radiation signal in air can be calculated as follows: (wavelength in air, or wavelength in vacuum) = speed of light/frequency, where frequency is the frequency of the radiation signal (MHz) and the speed of light can be taken as 3×108 m/s. The wavelength of the radiation signal in the medium can be calculated as follows: Wherein, ε is the relative dielectric constant of the medium. The wavelength in the embodiments of the present application generally refers to the dielectric wavelength, which can be the dielectric wavelength corresponding to the center frequency of the resonant frequency, or the dielectric wavelength corresponding to the center frequency of the working frequency band supported by the antenna. For example, assuming that the center frequency of the B1 uplink frequency band (resonant frequency is 1920MHz to 1980MHz) is 1955MHz, the wavelength can be the dielectric wavelength calculated using the frequency of 1955MHz. Not limited to the center frequency, "dielectric wavelength" can also refer to the dielectric wavelength corresponding to the non-center frequency of the resonant frequency or the working frequency band. For ease of understanding, the dielectric wavelength mentioned in the embodiments of the present application can be simply calculated by the relative dielectric constant of the medium filled on one or more sides of the radiator.

End/point: The "end/point" in the first end/second end/feeding end/grounding end/feeding point/grounding point/connection point of an antenna radiator should not be narrowly understood as an end point or end physically disconnected from other radiators, but can also be considered as a point or section on a continuous radiator. In one embodiment, an "end/point" may include a connection/coupling area on an antenna radiator that is coupled to other conductive structures. For example, the feeding end/feeding point may be a coupling area on an antenna radiator that is coupled to a feeding structure (for example, an area facing a portion of the feeding structure). For another example, the grounding end/grounding point may be a connection/coupling area on an antenna radiator that is coupled to a grounding structure.

Open end and closed end: In some embodiments, the terms open end and closed end refer to, for example, whether or not they are grounded. A closed end is grounded, while an open end is not. In one embodiment, an open end may also be referred to as a floating end, a free end, an open end, or an open-circuit end. In one embodiment, a closed end may also be referred to as a grounded end or a short-circuit end. It should be understood that in some embodiments, an open end may be coupled to other conductors to transfer coupled energy (which may be understood as transferring current).

In some embodiments, the open end and the closed end are, for example, relative to other conductors. The closed end is electrically connected to the other conductors, and the open end is not electrically connected to the other conductors.

To simply understand the "open end" of a radiator, one end of the radiator is spaced apart from the floor or coupled to the floor through a capacitive device, which can be regarded as the open end of the radiator.

To simply understand the "ground end" of the radiator, one end of the radiator is directly connected to the floor or coupled to the floor through an inductive device, which can be regarded as the ground end of the radiator.

In some embodiments, the "closed end" can also be understood from the perspective of current distribution. The closed end or the grounded end can be understood as a point with larger current on the radiator, or as a point with smaller electric field on the radiator. In one embodiment, coupling electronic devices (for example, inductive devices, etc.) through the closed end can maintain the current distribution characteristics of the larger current point/small electric field point. In one embodiment, opening a gap at or near the closed end (for example, a gap filled with insulating material) can maintain the current distribution characteristics of the larger current point/small electric field point.

In some embodiments, the understanding of "open end" can also be viewed from the perspective of current distribution. The open end or floating end can be understood as a point with low current on the radiator, or as a point with high electric field on the radiator. In one embodiment, coupling electronic devices (for example, capacitive devices, etc.) through the open end can maintain the current distribution characteristics of the low current point/high electric field point.

It should be understood that coupling electronic devices (for example, capacitors, inductors, etc.) to the radiator end at a gap (from the perspective of the radiator structure, it is similar to a radiator at an opening of an open end or a suspended end) can make the radiator end a point with larger current/smaller electric field. In this case, it should be understood that the radiator end at the gap is actually a closed end or a grounded end, etc.

The current same direction/reverse direction mentioned in the embodiments of the present application should be understood as the direction of the main current on the conductor on the same side is the same direction/reverse direction. For example, when stimulating a unidirectional distributed current on a conductor that is bent or ring-shaped (for example, the current path is also bent or ring-shaped), it should be understood that, for example, the main currents stimulated on the conductors on both sides of the ring conductor (for example, a conductor surrounding a gap, on the conductors on both sides of the gap) are opposite in direction, which still falls within the definition of unidirectional distributed current in this application. In one embodiment, the current same direction on a conductor can refer to the current on the conductor having no reversal point. In one embodiment, the current reverse on a conductor can refer to the current on the conductor having at least one reversal point. In one embodiment, the current same direction on two conductors can refer to the current on both conductors having no reversal point and flowing in the same direction. In one embodiment, the current reverse on two conductors can refer to the current on both conductors having no reversal point and flowing in opposite directions. The current same direction/reversal on multiple conductors can be understood accordingly.

Opposite/oppositely arranged: A and B being oppositely arranged may mean that A and B are arranged face-to-face. For example, when two radiators are oppositely arranged, at least a portion of the two radiators overlap along a certain direction. In one embodiment, the two oppositely arranged radiators are adjacent to each other, with no other radiators or conductive objects other than antenna structures positioned between them.

Impedance and Impedance Matching: Antenna impedance generally refers to the ratio of voltage to current at the antenna input. Antenna impedance is a measure of the antenna's resistance to electrical signals. Generally speaking, antenna input impedance is a complex number: the real part is called input resistance, denoted by Ri, and the imaginary part is called input reactance, denoted by Xi. Antennas whose electrical length is much smaller than the operating wavelength have large input reactance. For example, short dipole antennas have large capacitive reactance, while small loop antennas have large inductive reactance. The input impedance of a very thin half-wavelength dipole is approximately 73.1 + j42.5 ohms. In practical applications, for easier matching, it is generally desirable to have zero input reactance for a symmetrical dipole. The length of the dipole in this case is called the resonant length. The length of a resonant half-wavelength dipole is slightly shorter than half a wavelength in free space, generally estimated to be 5% shorter in engineering. The input impedance of an antenna is dependent on factors such as its geometry, size, feed point location, operating wavelength, and ambient environment. A thicker wire antenna exhibits a more gradual change in input impedance with frequency, resulting in a wider impedance bandwidth.

The primary purpose of studying antenna impedance is to achieve matching between the antenna and the transmission line. To match a transmitting antenna to a transmission line, the antenna's input impedance should be equal to the characteristic impedance of the transmission line. To match a receiving antenna to a receiver, the antenna's input impedance should be equal to the complex conjugate of the load impedance. Receivers typically have real impedance. When the antenna's impedance is complex, a matching network is required to remove the antenna's reactive component and equalize its resistive component.

When the antenna and transmission line are well matched, the power transmitted from the transmitter to the antenna or from the antenna to the receiver is maximized. In this case, there are no reflected waves on the transmission line, the reflection coefficient is zero, and the standing wave ratio is 1. The degree of antenna-to-transmission line matching is measured by the reflection coefficient or standing wave ratio at the antenna input. For a transmitting antenna, a poor match reduces the antenna's radiated power, increases transmission line losses, and decreases the line's power capacity. In severe cases, the transmitter's frequency may "pull," meaning the oscillation frequency changes.

Antenna pattern: Also known as radiation pattern. It is a graph showing how the relative field strength (normalized modulus) of the antenna's radiation field changes with direction at a certain distance from the antenna. It is usually represented by two mutually perpendicular plane patterns passing through the antenna's direction of maximum radiation.

Radiation efficiency refers to the ratio of the power radiated by an antenna into space (i.e., the power effectively converted into electromagnetic waves) to the active power input to the antenna. Active power input to the antenna = antenna input power - power loss. Power loss primarily includes return loss and metal ohmic loss and/or dielectric loss. Both metal loss and dielectric loss affect radiation efficiency.

Those skilled in the art will understand that efficiency is generally expressed as a percentage, which has a corresponding conversion relationship with dB. The closer the efficiency is to 0 dB, the better the efficiency of the antenna.

dB: Decibel, a logarithmic scale with a base of ten. The decibel scale is used only to measure the proportional relationship between one physical quantity and another; it itself has no physical dimension. For every 10-fold increase in the ratio between two quantities, the difference between them is expressed as 10 decibels. For example: A = 100, B = 10, C = 5, and D = 1. Then, A/D = 20dB; B/D = 10dB; C/D = 7dB; and B/C = 3dB. In other words, a 10dB difference between two quantities is a 10-fold difference, a 20dB difference is a 100-fold difference, and so on. A 3dB difference is a 2-fold difference.

dBi: Often mentioned together with dBd. dBi and dBd are units of power gain. Both are relative values, but they are referenced to different parameters. The reference for dBi is an omnidirectional antenna; the reference for dBd is a dipole. It is generally believed that dBi and dBd represent the same gain, with the value expressed in dBi being 2.15 dBi greater than the value expressed in dBd. For example, for an antenna with a gain of 16 dBd, its gain, when converted to dBi, is 18.15 dBi. Generally, the decimal places are ignored and the value is 18 dBi.

To facilitate understanding of the antenna structure provided in the embodiments of the present application, the following first introduces its application scenarios. The antenna structure provided in the embodiments of the present application is applicable to mobile terminals that adopt one or more of the following communication technologies: Bluetooth (BT) communication technology, global positioning system (GPS) communication technology, wireless fidelity (WiFi) communication technology, global system for mobile communications (GSM) communication technology, wideband code division multiple access (WCDMA) communication technology, long term evolution (LTE) communication technology, 5G communication technology, and other future communication technologies. In the embodiments of the present application, the mobile terminal can be, but is not limited to, a mobile terminal in any form, such as a straight-screen phone, a folding phone, a multi-folding mobile phone, a tablet computer, or a smart screen.

FIG1 is a schematic structural diagram of a mobile terminal provided in an embodiment of the present application. As shown in FIG1 , taking a mobile phone as an example, mobile terminal 010 may include: a cover 011, a display/module 012, a printed circuit board (PCB) 013, a middle frame 014, and a rear cover 015. It should be understood that in some embodiments, cover 011 may be a glass cover, or may be replaced with a cover made of other materials, such as an ultra-thin glass cover or a polyethylene terephthalate (PET) cover.

The cover plate 011 can be placed close to the display screen 012 , and the cover plate 011 mainly plays a role in protecting and preventing dust from the display screen 012 .

In one embodiment, the display screen 012 may include a liquid crystal display panel (LCD), a light emitting diode (LED) display panel, or an organic light-emitting semiconductor (OLED) display panel, etc., but this application does not impose any restrictions on this.

The middle frame 014 mainly supports the entire device. FIG1 shows that the PCB 013 is arranged between the middle frame 014 and the back cover 015. It should be understood that in one embodiment, the PCB 013 can also be arranged between the middle frame 014 and the display screen 012. This application does not limit this. Among them, the printed circuit board PCB 013 can adopt a flame-resistant material (FR-4) dielectric board, a Rogers dielectric board, a mixed dielectric board of Rogers and FR-4, and so on. Here, FR-4 is a code for a grade of flame-resistant material, and the Rogers dielectric board is a high-frequency board. PCB 013 carries electronic components, such as radio frequency chips.

Mobile terminal 010 may also include a battery (not shown). The battery may be disposed between middle frame 014 and back cover 015, or between middle frame 014 and display screen 012, although this application does not limit this. In some embodiments, PCB 013 is divided into a main board and a sub-board. The battery may be disposed between the main board and the sub-board. The main board may be disposed between middle frame 014 and the upper edge of the battery, and the sub-board may be disposed between middle frame 014 and the lower edge of the battery.

Mobile terminal 010 may further include a frame 016, which may be formed of a conductive material such as metal. Frame 016 may be connected between display screen 012 and back cover 015, and may be disposed circumferentially around the periphery of mobile terminal 010. In the present application, frame 016 may have four sides surrounding display screen 015 to secure display screen 015.

In one implementation, the bezel 016 primarily comprising a conductive material can be referred to as a conductive bezel or metal bezel of the mobile terminal 010, to accommodate a metal industrial design (ID). In one implementation, the outer surface of the bezel 016 is primarily comprised of a conductive material, such as a metal material, thereby creating the appearance of a metal bezel. In these implementations, the conductive portion of the outer surface of the bezel 016 can serve as an antenna radiator for the mobile terminal 010 and is generally referred to as a bezel antenna.

In another implementation, the outer surface of the frame 016 is mainly non-conductive material, such as plastic, to form the appearance of a non-metallic frame, which is suitable for non-metallic ID. In one implementation, the inner surface of the frame 016 may include a conductive material, such as a metal material. In this implementation, the inner surface of the frame 016 can be used as an antenna radiator of the mobile terminal 010. It should be understood that the radiator provided on the inner surface of the frame 016 (or the conductive material on the inner surface) can be set close to the non-conductive material of the frame 016 to minimize the internal space of the mobile terminal 010 occupied by the radiator, and to make the radiator closer to the outside of the mobile terminal 010, thereby achieving better signal transmission effect, and it can also be called a frame antenna. It should be noted that, in this application, the antenna radiator being disposed against the non-conductive material of the frame 016 means that the antenna radiator can be disposed closely against the inner surface of the non-conductive material of the frame 016, for example, the antenna radiator is disposed on a side edge of the frame 016. Alternatively, the antenna radiator being disposed against the non-conductive material of the frame 016 can also mean that the antenna radiator is embedded within the non-conductive material. Alternatively, the antenna radiator being disposed against the non-conductive material of the frame 016 can also mean that the antenna radiator is disposed close to the inner surface of the non-conductive material, for example, with a small gap between the antenna radiator and the inner surface of the non-conductive material. It should be understood that both the conductive material and the non-conductive material can be considered part of the frame 016.

In the present application, the middle frame 014 may include a frame 016. The middle frame 014 including the frame 016 is an integral part that can support the electronic devices in the whole machine. The cover 011 and the back cover 015 are respectively covered along both sides of the frame 016 to form the shell or housing of the mobile terminal 010. Alternatively, in the present application, the frame 016 may not be regarded as part of the middle frame 014. That is, in one embodiment of the present application, the frame 016 can be connected to the middle frame 014 and formed as one piece. In another embodiment of the present application, the frame 016 may include a protrusion extending into the interior of the mobile terminal 010 for connecting to the middle frame 014, wherein the protrusion of the frame 016 and the middle frame 014 can be connected to, but not limited to, by shrapnel, screws, welding, etc. In addition, in one embodiment, the cover 011, the back cover 015, the frame 016 and the middle frame 014 can be collectively referred to as the shell or housing of the mobile terminal 010. It should be understood that "shell or casing" can be used to refer to part or all of any one of the cover 011, the back cover 015, the frame 016 or the middle frame 014, or to refer to part or all of any combination of the cover 011, the back cover 015, the frame 016 or the middle frame 014.

In the present application, the back cover 015 can be a back cover made of metal material; it can also be a back cover made of non-conductive material, such as a glass back cover, a plastic back cover and other non-metallic back covers; it can also be a back cover including both conductive and non-conductive materials.

In one embodiment, the back cover 015 comprising a conductive material can replace the middle frame 014 and be integrated with the frame 016 to support the electronic components in the entire device.

In one embodiment, the conductive parts in the middle frame 014 and/or the back cover 015 can serve as a reference ground for the mobile terminal 010, wherein the frame 016 and PCB 013 of the mobile terminal can be electrically connected to the middle frame 014 to achieve grounding.

In one embodiment, the bezel 016 can at least partially serve as an antenna radiator to transmit and receive radio frequency signals. A gap can exist between this portion of the bezel serving as the radiator and other portions of the middle frame 014, or between the bezel and the middle frame 014, thereby ensuring a good radiation environment for the antenna radiator. In one embodiment, an aperture can be provided near this portion of the bezel serving as the antenna radiator. In one embodiment, the aperture can include an aperture provided within the interior of the mobile terminal 010, for example, an aperture that is not visible from the exterior surface of the mobile terminal 010. In one embodiment, the internal aperture can be formed by any one of the middle frame 014, the battery, the circuit board, the back cover 015, the display 012, or other internal conductive components, or by a combination of multiple components. For example, the internal aperture can be formed by a structural component of the middle frame 014. In one embodiment, the aperture can also include a slit/opening/opening provided in the bezel 016. In one embodiment, the slit/opening/opening in the bezel 016 can be a slit formed in the bezel 016, dividing the bezel 016 into two portions that are not directly connected. In one embodiment, the aperture may further include a slit/opening/hole provided on the back cover 015 or the display screen 012. In one embodiment, the back cover 015 includes a conductive material, and the aperture provided in the conductive material may be connected to the slit or crack of the frame 016 to form a continuous aperture on the exterior surface of the mobile terminal 010.

In one embodiment, the frame 016 includes a protrusion extending toward the interior of the mobile terminal 010 for connection to other portions of the middle frame 014 or to the middle frame 014 (in one embodiment, the protrusion may be integrally formed). In one embodiment, the protrusion includes a conductive material, which allows the protrusion to receive a feed signal or connect to a floor, thereby enabling the corresponding frame portion to receive/transmit radio frequency signals.

FIG. 1 only schematically illustrates some components included in the mobile terminal 010 , and the actual shapes, sizes, and structures of these components are not limited by FIG. 1 .

It should be understood that in the embodiments of the present application, the surface of the mobile terminal 010 where the display screen 012 is located can be considered as the front surface, the surface where the back cover 015 is located can be considered as the back surface, and the surface where the frame 016 is located can be considered as the side surface.

It should be understood that in the embodiments of the present application, it is considered that when the user holds the mobile terminal 010 (for example, the user holds the mobile terminal 010 and unlocks it, or for example, when the user holds the mobile terminal 010 vertically and faces the screen), the orientation of the mobile terminal 010 has a top, a bottom, and two sides located between the top and the bottom.

At present, the antenna in the mobile terminal 010 used to operate in the low-frequency band is generally called a frame antenna. The frame antenna is generally arranged on the side of the frame corresponding to the side of the mobile terminal and is arranged close to the bottom of the mobile terminal, wherein the low-frequency band may include at least one communication frequency band within 600MHz-1GHz.

Figure 2 is a schematic diagram of the configuration of a conventional frame antenna in a mobile terminal. Figure 2 illustrates the rear view of the mobile terminal, that is, the configuration of the frame antenna when the rear cover of the mobile terminal faces the user. In Figure 2, the radiator 1 of the frame antenna is disposed on a side of the frame 016, with one end of the radiator 1 being open and the other end being grounded. Furthermore, the physical length of the radiator 1 of the frame antenna is L1, and the electrical length of the radiator 1 having a physical length of L1 is approximately 1/4λ, where λ is the wavelength corresponding to the resonance generated by the frame antenna.

Continuing with FIG. 2 , the frame antenna further includes an impedance matching circuit 2 , which is connected to the feed point 101 of the radiator 1 . The impedance matching circuit 2 includes an inductor (not shown in FIG. 2 ) for impedance matching the frame antenna to adjust the resonant frequency generated by the frame antenna. Furthermore, the inductor of the impedance matching circuit has a relatively high inductance, for example, 15 nH.

The frame antenna in FIG2 further includes a tuning circuit 3, one end of which is grounded, and the other end of which is electrically connected between the impedance matching circuit 2 and the feed point 101. The capacitor in the tuning circuit 3 is used to tune the frequency of the frame antenna, and the capacitance of the capacitor in the tuning circuit 2 is relatively small, for example, 2 pF.

[Corrected 23.01.2025 in accordance with Article 91]
Figure 3 is a current distribution diagram of the frame antenna shown in Figure 2. Referring to Figure 3 , it can be seen that along the Y direction, that is, from the open end to the ground end of radiator 1, the current of the frame antenna gradually increases, and the current at the ground end of the frame antenna is the largest.

The aforementioned conventional frame antenna has high radiation efficiency in free space, but poor hand-grip performance. This is because the frame antenna radiates more energy toward the back cover, while less energy is radiated toward the display. Based on this, it can be understood that increasing the energy radiated toward the display is key to improving hand-grip performance.

In view of this, the present application provides an antenna structure that, by constructing the antenna structure as a co-directional slot antenna, achieves the purpose of aligning the electric fields generated by the various parts of the antenna structure's radiator, thereby facilitating tuning of the antenna structure's directional pattern toward the display screen. This ensures the antenna structure's radiation efficiency in free space while also optimizing its hand-grip performance. To facilitate understanding of the present application's technical solution, the antenna structure provided in the present application will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Referring to Figure 4 , Figure 4 is a simplified structural diagram of a mobile terminal provided in an embodiment of the present application. Figure 4 is also used to illustrate a rear view of the mobile terminal. In addition, Figure 4 illustrates the location of the antenna structure in the mobile terminal. Specifically, the antenna structure includes a radiator 1, which is disposed on a side of the frame 016. In the present application, the radiator 1 may be a conductive portion on the frame 016, for example, a portion of the conductive frame itself, or the radiator 1 may be a conductor on a non-conductive frame, which is not limited herein.

In the antenna structure provided in the present application, the radiator 1 includes a first branch 1a and a second branch 1b connected to each other, wherein the first branch 1a and the second branch 1b are arranged in a direction from the top to the bottom of the mobile terminal. In addition, the side of the frame 016 for setting the antenna structure has a slit 0161, and the first branch 1a extends to the above-mentioned slit 0161 in a direction away from the second branch 1b, then the end of the first branch 1a away from the second branch 1b is an open end, and the end of the second branch 1b away from the first branch 1a is grounded. The present application does not limit the grounding method of the end of the second branch 1b away from the first branch 1a. For example, as shown in FIG4 , the mobile terminal also includes a middle frame 014, then the end of the second branch 1b away from the first branch 1a can be connected to the middle frame 014 to achieve grounding through the grounding structure of the middle frame 014. Alternatively, when the frame 016 and the middle frame 014 are an integrally formed structure or the frame 016 and the middle frame 014 are connected through an inductive component, the end of the second branch 1b facing away from the first branch 1a can be grounded through the portion of the frame 016 used to connect to the middle frame 014.

The above is only an exemplary description of the grounding method of the end of the second branch 1b of the radiator 1 facing away from the first branch 1a. In other possible embodiments of the present application, any possible method can be used to connect the end of the second branch 1b facing away from the first branch 1a to the ground. They are not listed one by one here, but they should all be understood to fall within the scope of protection of this application.

It's worth noting that, in this application, there should be a clear clearance between the radiator 1 and the ground in the mobile terminal. Clearance refers to the vertical distance between the radiator and the ground. In antenna structures, the clearance directly affects signal transmission quality and coverage. Generally, the greater the clearance, the less signal obstruction and the better the transmission quality.

As can be seen from the above description of the ground in a mobile terminal, the middle frame 014 can serve as the ground in the mobile terminal. Therefore, in one embodiment of the present application, a clear gap is provided between the radiator 1 and the middle frame 014. Furthermore, a clear gap must also exist between the radiator 1 and other structures in the mobile terminal used to ground components therein to ensure a good radiation environment for the radiator 1.

4 , the first branch 1a includes a feeding point 101 , wherein a distance d between the feeding point 101 and the end of the first branch 1a away from the second branch 1b satisfies: d≤1/4×L1, and an exemplary d may be 1/16L1 or 1/8L1, etc.

In addition, in the present application, the antenna structure further includes an impedance matching circuit 2, which is connected to the feed point 101 and includes an inductor 201, a capacitor (not shown in FIG4 ), and a resistor (not shown in FIG4 ). It is worth mentioning that in the antenna structure provided in the present application, the inductor 201 in the impedance matching circuit 2 is used to perform impedance matching on the antenna structure, thereby achieving the purpose of adjusting the resonant frequency generated by the antenna structure.

The inductance mentioned in the embodiments of this application can be understood as lumped inductance and/or distributed inductance. Lumped inductance refers to an inductive component, such as an inductor; distributed inductance (or distributed inductance) refers to the equivalent inductance formed by a certain length of conductive material, such as the equivalent inductance formed by the curling or rotation of the conductor.

In a possible embodiment of the present application, the inductance value of the inductor 201 in the impedance matching circuit 2 is greater than or equal to 15 nH to meet the impedance matching requirement of the antenna structure.

In addition, in the present application, the electrical length λ1 of the first branch 1a is controlled to satisfy: 1/4×λ≤λ1＜3/8×λ. For example, λ1 can be 1/4λ to 5/16λ, etc., where λ is the wavelength corresponding to the resonance generated by the antenna structure. This is conducive to the antenna structure generating an antenna mode similar to a slot antenna.

It can be understood that since the radiator 1 of the antenna structure provided in the present application includes a first branch 1a and a second branch 1b, and the electrical length of the first branch 1a is basically the same as the electrical length of the entire radiator 1 of the border antenna shown in Figure 2 above, therefore, compared with the border antenna shown in Figure 2 above, the radiator 1 of the antenna structure provided in the present application has a larger electrical length, which is beneficial to increase the aperture of the antenna structure, thereby helping to improve the radiation performance of the antenna structure.

4 , in the present application, the connection point between the first branch 1 a and the second branch 1 b is grounded via an inductive structure, wherein the inductive structure may be an inductive device or a distributed inductor.

In addition, the physical length L1 of the first branch 1a and the physical length L2 of the second branch 1b satisfy: 4/5≤L1/L2≤4/3, that is, the physical length L1 of the first branch 1a is close to the physical length L2 of the second branch 1b, so that the antenna structure can be constructed into an antenna pattern analogous to a slot antenna, which is beneficial to optimizing the hand-holding performance of the antenna structure.

It is worth mentioning that when the physical length L1 of the first branch 1a and the physical length L2 of the second branch 1b are close, the corresponding electrical lengths of the two are also close. In a possible embodiment of the present application, the electrical length λ1 of the first branch 1a and the electrical length λ2 of the second branch 1b satisfy: |λ1-λ2|≤1/16×λ, where λ is the wavelength corresponding to the resonance generated by the antenna structure. In a specific embodiment of the present application, the electrical length λ1 of the first branch 1a and the electrical length λ2 of the second branch 1b can be equal.

[Corrected 23.01.2025 in accordance with Article 91]
In a specific embodiment, the physical length L1 of the first branch 1a and the physical length L2 of the second branch 1b can be equal. Referring to Figure 5, Figure 5 is a schematic diagram of the current flow direction of the antenna structure shown in Figure 4. Referring to Figure 5, it can be seen that the current on the first branch 1a and the current on the second branch 1b flow in the same direction, that is, the current on the first branch 1a flows along the open end toward the connection point of the first branch 1a and the second branch 1b, and the current on the second branch 1b flows along the connection point of the first branch 1a and the second branch 1b toward the ground end of the second branch 1b.

In addition, refer to Figure 6, which is a schematic diagram of the current amplitude distribution of the antenna structure shown in Figure 4. The dashed lines in Figure 6 illustrate the changes in the current amplitudes on the first branch 1a and the second branch 1b. As can be seen from Figure 6, the current amplitudes on the first branch 1a and the second branch 1b follow similar trends: that is, the current amplitude on the first branch 1a gradually increases, and the current amplitude on the second branch 1b gradually increases, along the direction of current flow.

[Corrected 23.01.2025 in accordance with Article 91]
Figure 7 is a schematic diagram of the electric field distribution of the antenna structure shown in Figure 4. As can be seen from Figure 7, the electric field generated by the first branch 1a and the electric field generated by the second branch 1b are in the same direction, both perpendicular to the frame 016 and toward the exterior of the mobile terminal. This facilitates tuning the antenna structure's in-screen directional pattern when held in a hand, thereby optimizing the antenna structure's hand-held performance.

Since the antenna structure provided in the present application is used to operate in a low-frequency band, and the low-frequency band includes at least one communication frequency band within 600MHz-1GHz. In order to be able to switch the various communication frequency bands within the above-mentioned low-frequency band so that the antenna structure can operate in the corresponding communication frequency band, as shown in Figure 4, the antenna structure provided in the embodiment of the present application may also include a tuning circuit 3. One end of the tuning circuit 3 is grounded, and the other end of the tuning circuit 3 is electrically connected between the impedance matching circuit 2 and the feeding point 101. In addition, the tuning circuit 3 includes at least one capacitor 301, which can be used to play a role in frequency tuning, that is, when the corresponding capacitor is electrically connected between the impedance matching circuit and the feeding point, the antenna structure can operate in the corresponding communication frequency band.

The capacitance mentioned in the embodiments of this application can be understood as lumped capacitance and/or distributed capacitance. Lumped capacitance refers to a capacitive component, such as a capacitor element; distributed capacitance (or distributed capacitance) refers to the equivalent capacitance formed by two conductive parts separated by a certain gap. Lumped capacitance can include a fixed capacitor C1 and/or a variable capacitor VAC; distributed capacitance can include interdigital capacitance and/or distributed capacitance formed in other forms.

In the present application, the capacitance of at least one capacitor 301 of the tuning circuit 3 is less than or equal to 2 pF. For example, the capacitance of at least one capacitor 301 of the tuning circuit 3 is 1 pF or 2 pF. This helps the antenna structure generate an antenna pattern similar to a slot antenna.

In a specific embodiment of the present application, the capacitance value of each capacitor of the tuning circuit 3 is less than or equal to 2 pF, which can be helpful in tuning the front-screen radiation pattern of the antenna structure in the hand-held state, thereby helping to optimize the hand-holding performance of the antenna structure.

It is understood that in the present application, when the tuning circuit 3 includes multiple capacitors 301, the multiple capacitors 301 are arranged in parallel. In this way, by electrically connecting different capacitors 301 between the impedance matching circuit 2 and the feed point 101, the antenna structure can be switched to a communication frequency band within the low frequency band.

The above only introduces some components of the antenna structure provided in this application. In addition, the antenna structure also includes a feeding circuit (not shown in Figure 4), wherein the impedance matching circuit 2 is electrically connected between the feeding circuit and the feeding point 101.

In this application, the feed circuit (also called the feed source) is a combination of all circuits used for receiving and transmitting radio frequency signals. The feed circuit may include a transceiver and an RF front end circuit (RF front end). In some cases, the "feed circuit" is understood in a narrow sense as a radio frequency integrated circuit (RFIC), and the RFIC can be considered to include an RF front end chip and a transceiver. The feed circuit has the function of converting radio waves (e.g., radio frequency signals) and electrical signals (e.g., digital signals). Generally, it is considered to be the RF part.

In some embodiments, the mobile terminal may also include a test socket (also referred to as an RF socket or RF test socket). The test socket can be used to insert a coaxial cable to test the characteristics of the RF front-end circuit or the antenna radiator through the cable. The RF front-end circuit can be considered as the circuit portion coupled between the test socket and the transceiver.

In some embodiments, the RF front-end circuit may be integrated into a RF front-end chip in the mobile terminal, or the RF front-end circuit and the transceiver may be integrated into a RF chip in the mobile terminal.

It should be understood that any two of the first/second/...Nth feeding circuits in the present application can share the same transceiver, for example, transmitting signals through a radio frequency channel in a transceiver (for example, a port (pin) of a radio frequency chip); they can also share a radio frequency front-end circuit, for example, processing signals through a switch or amplifier in a radio frequency front-end.

It should also be understood that two feeding circuits in the first/second/...Nth feeding circuit in the present application usually correspond to two radio frequency test sockets in the mobile terminal.

As described above in the present application regarding the specific configuration of the antenna structure, the connection point between the first branch 1a and the second branch 1b is grounded via the inductive structure 4. This application does not specify the specific grounding method for the inductive structure 4. For example, the inductive structure 4 is connected to the middle frame 014, thereby connecting the connection point between the first branch 1a and the second branch 1b to the middle frame 014 via the inductive structure 4.

Continuing with FIG4 , since the antenna structure provided in this application operates in a low-frequency band, the antenna structure is positioned near the bottom of the mobile terminal. Furthermore, since the battery is typically positioned near the bottom of a mobile terminal and is housed in a battery compartment 0141 of the midframe 014, it can be seen that the battery compartment 0141 of the midframe 014 is positioned near the bottom of the mobile terminal.

As shown in Figure 4, in one possible embodiment of the present application, the radiator 1 of the antenna structure is located on one side of the frame 016, facing the battery compartment 0141. Furthermore, along the direction from the second branch 1b to the first branch 1a, the connection point between the first branch 1a and the second branch 1b is lower than the top of the battery compartment 0141. This helps improve the utilization of the portion of the frame 016 facing the battery compartment 0141 and increases the physical length of the radiator 1, thereby improving the aperture of the antenna structure.

In a possible embodiment of the present application, along the direction from the second branch 1b to the first branch 1a, the open end of the first branch 1a can also be made lower than the top of the battery compartment 0141, so that the part of the frame 016 opposite to the battery compartment 0141 can be fully utilized, and the effect of expanding the aperture of the antenna structure can still be achieved.

Since the battery compartment 0141 can also be a grounding structural component, in the present application, the inductive structure 4 can include a grounding rib 401, one end of which is connected to the connection point between the first branch 1a and the second branch 1b, and the other end of the grounding rib 401 is connected to the battery compartment 0141, that is, the other end of the grounding rib 401 is connected to the middle frame 014.

The present application does not limit the specific configuration of the grounding rib 401. It can be exemplarily a section of a strip-shaped bent conductor, such as a strip-shaped metal conductor. In addition, the grounding rib 401 can be either a rigid structural member or a flexible structural member.

Furthermore, it is understood that to ensure battery capacity, the battery is typically larger, and thus the battery compartment 0141 is larger, which results in a smaller space between the battery compartment 0141 and the side of the frame 016. Based on this, in one possible embodiment of the present application, the grounding rib 401 of the inductive structure 4 can be integrally formed with the middle frame 014. This effectively reduces the space occupied by the inductive structure 4, thereby avoiding any impact on the size of the battery compartment 0141.

It is worth mentioning that since the frame 016 can also be integrally formed with the middle frame 014, in a possible embodiment of the present application, the grounding rib 401 of the inductive structure 4, the middle frame 014 and the frame 016 can be an integrally formed structure. This can ensure the reliability of the connection point between the first branch 1a and the second branch 1b being grounded through the grounding rib 401, and is also beneficial to improving the structural integration of the mobile terminal. In addition, it can also facilitate the control of the space occupied by the grounding rib 401 to reserve sufficient setting space for the battery, thereby meeting the battery capacity requirements.

In another possible embodiment of the present application, the inductive structure 4 can also be an independent structural component. For example, the inductive structure 4 may include a printed circuit board (PCB) and at least two conductive connecting parts, wherein the at least two conductive connecting parts are connected through metal traces of the printed circuit board, so that at least one conductive connecting part can be connected to the connection point of the first branch 1a and the second branch 1b, and at least one conductive connecting part can be connected to the battery compartment 0141.

In another possible embodiment of the present application, the inductive structure 4 may further include a flexible printed circuit (FPC), and the flexible printed circuit can be flexibly bent and arranged between the frame 016 and the battery compartment 0141. In addition, one end of the flexible printed circuit can be connected to the connection point of the first branch 1a and the second branch 1b, and the other end of the flexible printed circuit can be connected to the battery compartment 0141.

The above is only some exemplary explanations of the setting method of the inductive structure 4. Based on this, the specific setting method of the inductive structure 4 can also be adaptively modified according to the specific application scenario. They are not listed one by one here, but they should all be understood to fall within the scope of protection of this application.

Figure 8 compares the free-space radiation efficiency of the antenna structure provided by the present invention and the conventional frame antenna shown in Figure 2. The solid line represents the free-space radiation efficiency of the antenna structure provided by the present invention, while the dashed line represents the free-space radiation efficiency of the conventional frame antenna shown in Figure 2. As can be seen from Figure 8, the free-space radiation efficiency of the antenna structure provided by the present invention is similar to that of the conventional frame antenna shown in Figure 2.

In addition, referring to Figure 9, Figure 9 is a comparison of the radiation efficiency of the antenna structure provided by the embodiment of the present application and the existing frame antenna shown in Figure 2 when held in the hand. The solid line represents the radiation efficiency of the antenna structure provided by the present application when held in the hand, and the dashed line represents the radiation efficiency of the existing frame antenna shown in Figure 2 when held in the hand. As can be seen from Figure 9, when held in the hand, the radiation efficiency of the antenna structure provided by the embodiment of the present application is higher than that of the existing frame antenna shown in Figure 2.

As can be understood from the above, in this application, by constructing the antenna structure into an antenna pattern similar to that of a co-directional slot antenna, the currents in the first branch 1a and the second branch 1b of the radiator are aligned, thereby aligning the electric fields in the first branch 1a and the second branch 1b. This facilitates tuning the antenna structure's in-front-screen pattern when held in a hand, thereby optimizing the antenna structure's hand-held performance.

The above are only specific embodiments of the present application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims (14)

An antenna structure, comprising a radiator and an impedance matching circuit, wherein: The radiator includes a first branch and a second branch connected to each other, wherein an end of the first branch facing away from the second branch is an open end, the first branch includes a feeding point, an end of the second branch facing away from the first branch is grounded, and a connection point between the first branch and the second branch is grounded via an inductive structure; The physical length L1 of the first branch and the physical length L2 of the second branch satisfy: 4/5≤L1/L2≤4/3; The distance d between the feeding point and the end of the first branch facing away from the second branch satisfies: d≤1/4×L1; The impedance matching circuit is electrically connected to the feeding point, and the impedance matching circuit includes an inductor. The antenna structure according to claim 1 is characterized in that the antenna structure is used to operate in a low frequency band, and the low frequency band includes at least one communication frequency band within 600 MHz-1 GHz. The antenna structure according to claim 2, wherein the inductance of the inductor is greater than or equal to 15nH. The antenna structure according to any one of claims 1 to 3 is characterized in that the antenna structure further includes a tuning circuit, one end of the tuning circuit is grounded, and the other end of the tuning circuit is electrically connected between the impedance matching circuit and the feeding point; the tuning circuit includes at least one capacitor. The antenna structure according to claim 4, wherein the capacitance of the at least one capacitor is less than or equal to 2 pF. The antenna structure according to claim 4 or 5 is characterized in that the tuning circuit includes a plurality of the capacitors, and the plurality of the capacitors are arranged in parallel. The antenna structure according to any one of claims 1 to 6, characterized in that the antenna structure further comprises a feeding circuit, and the impedance matching circuit is electrically connected between the feeding circuit and the feeding point. A mobile terminal, characterized in that it includes a frame and the antenna structure according to any one of claims 1 to 7, wherein the frame is arranged around the outer circumference of the mobile terminal, and the radiator of the antenna structure is arranged on a side of the frame. The mobile terminal according to claim 8 is characterized in that the mobile terminal further includes a middle frame, the middle frame is located within the interval formed by the border, the end of the second branch facing away from the first branch is connected to the middle frame, and the connection point between the first branch and the second branch is connected to the middle frame through the inductive structure. The mobile terminal as described in claim 9 is characterized in that the middle frame includes a battery compartment, the radiator is located on a side of one of the side edges of the frame facing the battery compartment, and along the direction from the second branch to the first branch, the connection point between the first branch and the second branch is lower than the top of the battery compartment. The mobile terminal according to claim 10 is characterized in that the inductive structure includes a grounding rib, the grounding rib is located between the battery compartment and the radiator, one end of the grounding rib is connected to the connection point of the first branch and the second branch, and the other end of the grounding rib is connected to the middle frame. The mobile terminal according to claim 11, wherein the grounding rib, the middle frame and the frame are an integrally formed structure. The mobile terminal according to claim 10, wherein the inductive structure is an independent structural component, and the inductive portion of the inductive structure is connected to the connection point between the first branch and the second branch, and is connected to the middle frame. The mobile terminal according to any one of claims 9 to 13, wherein a clear space exists between the radiator and the middle frame.