HK1260592B - Multi-band power amplifier - Google Patents

Description

Multiband power amplifier

This application is a divisional application of patent application 201610196053.4 entitled "multi-band power amplifier" filed 2016, 31/03.

Cross Reference to Related Applications

This application claims priority from U.S. provisional application No. 62/140,925 entitled "Multi-BAND Power Amplifier" filed on 31/03/2015. The contents of each of the above-identified applications are hereby expressly incorporated herein by reference in their entirety for all purposes.

Technical Field

The present application relates generally to power amplifiers.

Background

To boost the efficiency of power amplifiers while maintaining good linearity, many designers of linear power amplifiers have adopted class F and inverse class F power amplifiers. However, maintaining operation of class F and inverse class F power amplifiers often requires the use of harmonic termination (harmonic termination) at the output of the power amplifier. Maintaining good harmonic termination across a wide frequency bandwidth while achieving higher maximum power amplifier efficiency may be difficult. For example, in general, the efficiency of a power amplifier decreases as the bandwidth increases.

Disclosure of Invention

In some embodiments, the present application relates to a power amplifier module. The power amplifier module includes: a power amplifier including an output stage, the power amplifier configured to receive a signal. The power amplifier module further comprises: a first programmable harmonic termination circuit in electrical communication with an output stage of the power amplifier, the first programmable harmonic termination circuit comprising a first plurality of capacitors and a first plurality of switches, at least one of the first plurality of capacitors in electrical communication with at least one of the first plurality of switches. The power amplifier module further comprises: a controller configured to alter a configuration of the first plurality of switches of the first programmable harmonic termination circuit based at least in part on a second harmonic frequency of the signal.

In some embodiments, the power amplifier module further comprises: a second programmable harmonic termination circuit in electrical communication with the output stage of the power amplifier, the second programmable harmonic termination circuit including a second plurality of capacitors and a second plurality of switches.

In some embodiments, at least one of the second plurality of capacitors is in electrical communication with at least one of the second plurality of switches, the controller further configured to alter the configuration of the second plurality of switches of the second programmable harmonic termination circuit based at least in part on a third harmonic frequency of the signal.

In some embodiments, in response to a control signal associated with class F operation, the controller is further configured to alter a configuration of the first plurality of switches of the first programmable harmonic termination circuit to short circuit a second harmonic frequency of the signal and alter a configuration of the second plurality of switches of the second programmable harmonic termination circuit to present an open circuit impedance to a third harmonic frequency of the signal.

In some embodiments, in response to a control signal associated with inverse class F operation, the controller is further configured to alter a configuration of the first plurality of switches of the first programmable harmonic termination circuit to present an open circuit impedance to a second harmonic frequency of the signal and alter a configuration of the second plurality of switches of the second programmable harmonic termination circuit to short circuit a third harmonic frequency of the signal.

In some embodiments, the controller is further configured to alter a configuration of the first plurality of switches of the first programmable harmonic termination circuit based at least in part on the selected operating class of the power amplifier.

In some embodiments, the power amplifier supports multiple configurations.

In some embodiments, the power amplifier supports at least two of the following configurations: a class F configuration, an inverse class F configuration, a class E configuration, or a class J configuration.

In some embodiments, the power amplifier module further comprises an output impedance matching network in electrical communication with the output stage of the power amplifier.

In some embodiments, the power amplifier module further comprises a low pass filter in electrical communication with the output stage of the power amplifier.

In some embodiments, the power amplifier module does not include an output impedance matching network in electrical communication with an output stage of the power amplifier.

In some embodiments, the present application relates to a wireless device. The wireless device includes: a plurality of load lines, at least some of the load lines corresponding to different communication frequency bands. The wireless device further comprises: a switch network configured to electrically connect a load line from the plurality of load lines to the power amplifier. The wireless device further comprises: a power amplifier module comprising a power amplifier, a first programmable harmonic termination circuit in electrical communication with an output stage of the power amplifier, the power amplifier configured to receive a signal, the first programmable harmonic termination circuit comprising a first plurality of capacitors and a first plurality of switches, at least one of the first plurality of capacitors in electrical communication with at least one of the first plurality of switches, and a controller configured to alter a configuration of the first plurality of switches of the first programmable harmonic termination circuit based at least in part on a second harmonic frequency of the signal.

In some embodiments, the power amplifier module further comprises: a second programmable harmonic termination circuit in electrical communication with the output stage of the power amplifier, the second programmable harmonic termination circuit including a second plurality of capacitors and a second plurality of switches.

In some embodiments, at least one of the second plurality of capacitors is in electrical communication with at least one of the second plurality of switches, the controller further configured to alter the configuration of the second plurality of switches of the second programmable harmonic termination circuit based at least in part on a third harmonic frequency of the signal.

In some embodiments, the power amplifier supports multiple operating classes.

In some embodiments, the present application relates to a power amplifier module. The power amplifier module includes: a multi-stage power amplifier including at least a first stage and a second stage, the multi-stage power amplifier configured to receive a signal. The power amplifier module further comprises: an inter-stage programmable harmonic termination circuit located between the first stage and the second stage, the inter-stage programmable harmonic termination circuit comprising a plurality of capacitors and a plurality of switches, at least one of the plurality of capacitors in electrical communication with at least one of the plurality of switches. The power amplifier module further comprises: a controller configured to alter a configuration of the plurality of switches of the inter-stage programmable harmonic termination circuit based at least in part on a harmonic frequency of the signal.

In some embodiments, the second stage is an output stage of the power amplifier.

In some embodiments, the harmonic frequency of the signal is one of a second harmonic frequency or a third harmonic frequency.

In some embodiments, the controller is further configured to alter a configuration of the plurality of switches with respect to one of the second harmonic frequency or the third harmonic frequency based at least in part on a particular class of operation of the multi-stage power amplifier.

In some embodiments, the particular class of operation of the amplifier corresponds to a communication frequency band from among a plurality of communication frequency bands supported by the multi-stage power amplifier.

In some embodiments, the power amplifier module further comprises: an output stage programmable harmonic termination circuit located after and in electrical communication with the second stage.

In some embodiments, the output stage programmable harmonic termination circuit supports multiple operational classes of the multi-stage power amplifier.

In some embodiments, the present application relates to a wireless device. The wireless device includes: a plurality of load lines, at least some of the load lines corresponding to different communication frequency bands. The wireless device further comprises: a switch network configured to electrically connect a load line from the plurality of load lines to the power amplifier. The wireless device further comprises: a power amplifier module comprising a multi-stage power amplifier including at least a first stage and a second stage and configured to receive a signal, an inter-stage programmable harmonic termination circuit located between the first stage and the second stage and including a plurality of capacitors and a plurality of switches, at least one of the plurality of capacitors in electrical communication with at least one of the plurality of switches, and a controller configured to alter a configuration of the plurality of switches of the inter-stage programmable harmonic termination circuit based at least in part on a harmonic frequency of the signal.

In some embodiments, the second stage is an output stage of the power amplifier.

In some embodiments, the harmonic frequency of the signal is one of a second harmonic frequency or a third harmonic frequency.

In some embodiments, the controller is further configured to alter a configuration of the plurality of switches with respect to one of the second harmonic frequency or the third harmonic frequency based at least in part on a particular class of operation of the multi-stage power amplifier.

In some embodiments, the power amplifier module further comprises: a programmable harmonic termination circuit in electrical communication with an output of the second stage.

Drawings

Throughout the drawings, reference numerals are repeated to indicate correspondence between referenced elements. The drawings are provided to illustrate embodiments of the inventive subject matter described herein and not to limit the scope thereof.

Fig. 1 is a block diagram of an example of a distributed switched harmonic termination circuit.

Fig. 2 is a circuit diagram of one example of a distributed switched harmonic termination circuit.

Fig. 3 is a circuit diagram of one example of a switched harmonic termination circuit supporting multiple power amplifier operating classes.

Fig. 4 is a circuit diagram of one example of a switched harmonic termination circuit supporting multiple power amplifier operation classes with shared circuit elements.

Fig. 5 is a circuit diagram of one example of a switched harmonic termination circuit for class F operation of a power amplifier.

Fig. 6 is a circuit diagram of one example of a switched harmonic termination circuit for inverse class F operation of a power amplifier.

Fig. 7 is a circuit diagram of one example of a switched harmonic termination circuit for class E operation of a power amplifier.

Fig. 8 is a block diagram of one example of a power amplifier module that may include a multi-band power amplifier.

Fig. 9 is a block diagram of one example of a wireless device that may include the power amplifier module of fig. 8.

Fig. 10 is a flowchart of one example of a power amplifier class selection process.

Detailed Description

To boost the efficiency of power amplifiers while maintaining good linearity, many designers of linear power amplifiers have adopted class F and inverse class F power amplifiers. However, maintaining operation of class F and inverse class F power amplifiers often requires the use of harmonic terminations at the output of the power amplifier. Maintaining good harmonic termination across a wide frequency bandwidth while achieving higher maximum power amplifier efficiency can be difficult. For example, in general, the efficiency of a power amplifier decreases as the bandwidth increases.

One approach for maintaining power amplifier efficiency across a wide bandwidth is to use several power amplifiers to cover the entire desired bandwidth. However, including multiple power amplifiers within a design may increase the cost of the wireless device and require more space for each power amplifier. In addition, wireless devices that support multiple communication technologies (such as 3G and 4G technologies) also require multiple sets of power amplifiers to cover the selected bandwidth for each communication technology.

Also, the output impedance of the power amplifier at the collector is typically about 3 ohms (ohms). However, the load line is typically at 50 ohms. Thus, a transformer (transformer) is typically used to boost the battery voltage and help match the output impedance of the power amplifier to the load line impedance. However, in many cases, the transformation is performed at a specific frequency, typically a narrower frequency band, for example because the transformation occurs at a single frequency.

Embodiments described herein use a switched harmonic termination network to enable a power amplifier to support multiple classes of operation across a wide bandwidth. In some embodiments, the number of power amplifiers included in a wireless device may be reduced by including a programmable switched harmonic termination network. For example, in some cases, a wireless device may include two or even one power amplifier that supports multiple types of operation. In addition, the switched harmonic termination network enables the power amplifier to support multiple operating frequency bands.

Additionally, the embodiments described herein use a power amplifier design that can boost the voltage at the collector of the power amplifier to, for example, about 10V. By boosting the voltage, the output impedance of the power amplifier can be close to 50 ohms. Thus, in some cases, it may not be necessary to transform the voltage, and the transformer may be omitted. Furthermore, the size of the output impedance matching network in electrical communication with the output stage of the power amplifier and the amount of impedance transformation it provides may be significantly reduced, and in some cases, the output impedance matching network may even be eliminated or replaced with a low pass filter. Examples of power amplifiers that may be used with the embodiments described herein are described in the following patent applications: US provisional application No. 62/116,448 entitled "REDUCED POWER AMPLIFIER SIZE THROUGH ELEMINATION OF MATCHING NETWORK" filed on 15.02/2015, US provisional application No. 62/116,449 entitled "ENHANCED POWER AMPLIFIER EFFICIENCY THIUGH ELEMINATION OF MATCHING NETWORK" filed on 15.02/2015, US provisional application No. 62/116,450 entitled "MULTI-BAND POWER AMPLIFICATION SYSTEM HAVING ENHANCED EFFICIENCY THROUGH ELEMINATION OF BAND SELECTION SWITCH" filed on 15.2015, U.S. provisional application No. 62/116,451 entitled "MULTI-BAND DEVICE HAVING MULTI minor dimensional cover paste POWER AMPLIFIERS" filed 15.02/2015 and U.S. provisional application No. 62/116,452 entitled "RADIO-FREQUENCY POWER AMPLIFIERS DRIVEN BY BOOST CONVERTER" filed 15.2015, the disclosures of each of which are hereby incorporated BY reference in their entirety.

Advantageously, the use of the switched harmonic termination circuits described herein enables the power amplifier to support operation across a larger bandwidth in certain embodiments than previously designed power amplifiers. Furthermore, in some embodiments, the use of a switched harmonic termination circuit enables the power amplifier to provide multiple classes of operation. Thus, in some embodiments, a wireless device that previously may require several power amplifiers may use fewer power amplifiers (such as two power amplifiers or one power amplifier) while supporting the same type of operation and frequency band.

Exemplary distributed switching harmonic termination circuits

Fig. 1 is a block diagram of one example of a distributed switched harmonic termination circuit. Fig. 1 illustrates a portion of a circuit 100 that may be included in a power amplifier module. The circuit 100 includes a Power Amplifier (PA) 102. In some cases, each element of circuit 100 may be included as part of power amplifier 102. Typically, but not necessarily, the power amplifier 102 is a multi-stage power amplifier, which may include multiple stages (e.g., two, three, five, or ten stages, etc.). In the particular example illustrated in fig. 1, the power amplifier 102 is a two-stage amplifier that includes an input stage 106 and an output stage 104. The transistors of the input stage 106 and the output stage 104 may be Bipolar Junction Transistors (BJTs), Heterojunction Bipolar Transistors (HBTs), gallium arsenide (GaAs) transistors, Field Effect Transistors (FETs), or any other type of transistor that may be used in a power amplifier design.

Although not shown, it is understood that the power amplifier 102 may also include one or more bias circuits for biasing the transistor stages of the power amplifier 102. In some embodiments, different bias values may be applied to the transistor stages (e.g., input stage 106 and output stage 104) based on the particular communication standard (e.g., 2G, 3G, 4G, or 4G LTE) used at a particular point in time. Moreover, PA102 may include a PA design that reduces or eliminates the need for an output impedance matching network for matching the impedance of the load line, such as described in the provisional applications incorporated by reference above (U.S. provisional application No. 62/116,448, U.S. provisional application No. 62/116,449, U.S. provisional application No. 62/116,450, U.S. provisional application No. 62/116,451, and U.S. provisional application No. 62/116,452).

As shown in fig. 1, the power amplifier 102 includes an inter-stage switched harmonic termination 110 (sometimes referred to as or including a harmonic notch filter). Circuit 100 also includes an output stage switch harmonic termination 108 (sometimes referred to as or including a harmonic notch filter) electrically connected to the collector of output stage transistor 104. In some embodiments, the inter-stage switch harmonic termination 110 and the output stage switch harmonic termination 108 may work in combination to provide distributed harmonic termination for one or more harmonics of the signal. Advantageously, in certain embodiments, the use of the inter-stage switch harmonic termination 110 may improve the efficiency of the output stage 104.

As described above, the power amplifier 102 may include multiple stages. Where the power amplifier 102 includes more than two stages, such as three or four stages, the switched harmonic terminations may be distributed among multiple inter-stage harmonic terminations as well as the output stage harmonic termination 108. For example, interstage switch harmonic terminations may exist between the first and second stages, and between the second and third stages of a three-stage power amplifier. However, for many power amplifiers, the signal is small at a transistor stage preceding the output transistor stage. Thus, in many such cases, the inter-stage switch harmonic termination may only be present before the output stage of the power amplifier.

The switched harmonic terminals 110 and 108 may each include circuitry for processing the second harmonic signal (2F0) and the third harmonic signal (3F 0). In some cases, the switched harmonic terminations 110 and 108 may be configured to be short or open circuit impedances to one or both of the second harmonic signal and the third harmonic signal. Typically, but not necessarily, the switched harmonic terminals 110 and 108 may be configured to be a short circuit for one of the second harmonic signal or the third harmonic signal and an open circuit impedance for the other of the second harmonic signal or the third harmonic signal. In general, the switched harmonic terminals 110 and 108 are configured to process second and/or third harmonic signals of a signal received at an RF input to the power amplifier 102. Other harmonics of the signal are generally ignored. However, in some cases, one or more of the switched harmonic terminals 108 and 110 may be configured to process other harmonics of the signal received at the RF input to the power amplifier 102.

Advantageously, electrically connecting one or more harmonic terminals to the power amplifier may, in some embodiments, improve the efficiency of the power amplifier, and may shape the voltage and current waveforms to result in an improved amplifier. For example, an improved class F amplifier can be obtained by: the voltage waveform is shaped more like a square wave and the current waveform is shaped like a half sine wave, so that the amount of current and voltage across the transistors is reduced and the power dissipated in the output transistor is reduced while providing the desired output power.

A class F power amplifier is often used because it can have a relatively flat relative output power gain (gain over output power) and a small relative output power phase shift (phase shift over output power) until the PA reaches the compression point (compression point). Thus, class F amplifiers can be used for linear PAs. However, embodiments herein may use other classes of PAs such as, but not limited to, class E, class J, or inverse class F. Also, while multiple harmonic terminations may be included to short circuit even harmonics and provide open circuit impedance for odd harmonics, generally, harmonic terminations are provided for only the second and third harmonics, for example, because other harmonics have less of an impact on the received signal and the design may be simplified. However, harmonic termination circuits for other harmonics may be included.

Typically, the fundamental frequency may be handled by an output impedance matching network or a low pass filter. In other cases, a fundamental frequency may be provided as the RF output of the circuit 100.

In some embodiments, the circuit 100 further includes an output impedance matching network 112. In some cases, the output impedance matching network 112 may comprise a dynamic output impedance matching network. For example, in some embodiments, the output impedance matching network 112 may include one or more of the embodiments described in U.S. provisional application No. 62/057,451 entitled "AUTOMATIC IMPEDANCE MATCHING USING TRUE POWER INFORMATION," filed on 30/09/2014, which is incorporated herein by reference in its entirety. Alternatively, the output impedance matching network 112 may be replaced by a low pass filter. In some cases, the circuit 100 may include an output impedance matching network 112 and a low pass filter.

Fig. 2 is a circuit diagram of one example of a distributed switched harmonic termination circuit 200. For ease of illustration, reference numeral 102 and the corresponding dashed box of fig. 1 are omitted from fig. 2, 3 and 4. It should be understood, however, that transistor stages 106 and 104 are part of power amplifier 102, such as illustrated with respect to fig. 1.

As shown in fig. 2, the inter-stage switch harmonic termination 110 may include an inductor L0 ' and a plurality of capacitors C0 ' through Cn '. Further, the inter-stage switch harmonic termination 110 may include a plurality of switches that may be used to electrically connect one or more of the capacitors C0 ' through Cn ' to the inductor L0 ' and the base of the output stage transistor 104. Although no switch is shown between capacitor C0 'and inductor L0', it should be understood that such a switch may be present. Similarly, although no switches are illustrated between the interstage switch harmonic terminal 110 and the power amplifier, it is understood that such switches may be present.

As with the inter-stage switched harmonic terminal 110, the output stage switched harmonic terminal 108 may include an inductor L0, a plurality of capacitors C0 through Cn, and one or more switches, such as switches S1 through Sn. The switches S1-Sn may electrically connect one or more of the capacitors C0-Cn to the inductor L0 and the collector of the output stage transistor. Although no switch is illustrated between capacitor C0 and inductor L0, it is understood that such a switch may be present. Similarly, although no switches are illustrated between the output stage switch harmonic termination 108 and the output stage of the power amplifier, it is understood that such switches may be present. The switch may be a silicon-on-insulator (SOI) switch.

Advantageously, in some embodiments, by including switched capacitors in the harmonic termination circuits 108 and 110, the harmonic termination circuits may be optimized for a particular frequency band. Furthermore, the ability to alter harmonic termination circuits across frequency bands enables wireless devices that previously included, for example, eight PAs or low and mid-band operation to include two or one PA. Also, the inclusion of the switchable capacitor enables the harmonic termination circuit to be dynamically tuned for different operating frequencies based on manufacturer specifications and/or the particular communication network with which the wireless device including the PA102 wirelessly communicates.

Note that in some existing power amplifier designs, different impedances cannot be switched in for the harmonic termination circuits because the output impedance of the PA is too low compared to the load line. Advantageously, in certain embodiments, the higher output impedance of the PA described in the previously incorporated provisional applications (U.S. provisional application No. 62/116,448, U.S. provisional application No. 62/116,449, U.S. provisional application No. 62/116,450, U.S. provisional application No. 62/116,451, and U.S. provisional application No. 62/116,452) enables the use of switched harmonic termination, thereby enabling the PA to support multiple classes of operation and a wider operating frequency band.

Each of the inter-stage switch harmonic terminal 110 and the output stage switch harmonic terminal 108 may receive one or more control signals from a controller (not shown). These control signals may be used to control the state of the switches of the harmonic termination circuit. Advantageously, in certain embodiments, the ability to modify the harmonic termination circuits 108 and 110 enables the power amplifier to be used for multiple frequency bands. Furthermore, in some embodiments, modifying the capabilities of the harmonic termination circuits 108 and 110 enables the power amplifier to satisfy multiple classes of operation (e.g., class E, class J, class F, or inverse class F, etc.).

Exemplary switched harmonic termination-multiple PA operation classes

Fig. 3 is a circuit diagram of one example of a switched harmonic termination circuit supporting multiple power amplifier operating classes. In the example shown in fig. 3, the circuit 300 supports both class F and inverse class F operations. Circuit 300 includes harmonic termination circuit 302 and harmonic termination circuit 304.

Harmonic termination circuit 302 is configured to support class F operation of the power amplifier. In some embodiments, harmonic termination circuit 302 is configured to process the second harmonic 2F0 of the RF input signal received by the power amplifier. As the frequency of the signal received by the power amplifier changes, the harmonic frequencies also change. The harmonic termination circuit 302 may be modified by electrically connecting or disconnecting one or more of the capacitors C1 through Cn to adjust the harmonic termination for the second harmonic of the received signal. In addition, harmonic circuit 302 includes an inductor L1 in series with capacitors C1 through Cn to create an LC circuit.

The harmonic termination circuit 304 is configured to support inverse class F operation of the power amplifier. In certain embodiments, harmonic termination circuit 304 is configured to process the third harmonic 3F0 of the RF input signal received by the power amplifier. The harmonic termination circuit 304 may be modified by electrically connecting or disconnecting one or more of the capacitors C1 'through Cn' to adjust the harmonic termination for the third harmonic of the received signal. In addition, the harmonic circuit 304 includes an inductor L1 ' in series with capacitors C1 ' to Cn ' to create an LC circuit.

Further, the circuit 300 may include additional circuitry (circuitry) that may be included as part of the output impedance matching network 112, or separately, for handling other harmonics. For example, where the power amplifier operates as a class F power amplifier, the circuit 300 may use additional circuitry to handle the third harmonic of the RF input signal. Similarly, where the power amplifier operates as an inverse class F power amplifier, the circuit 300 may use additional circuitry to handle the second harmonic of the RF input signal.

Fig. 4 is a circuit diagram of one example of a switched harmonic termination circuit supporting multiple power amplifier operation classes with shared circuit elements. In the example shown in fig. 4, similar to circuit 300, circuit 400 supports both class F and inverse class F operations. The circuit 400 includes a combined harmonic termination circuit 402 capable of supporting multiple power amplifier operating classes. In the particular example shown in fig. 4, combined harmonic termination circuit 402 includes a harmonic termination circuit 404 that supports class F operation and a harmonic termination circuit 406 that supports inverse class F operation.

As shown in fig. 4, harmonic termination circuits 404 and 406 share inductor L1. In some implementations, harmonic termination circuits 404 and 406 may share one or more capacitors. Advantageously, in certain embodiments, by harmonic termination circuits 404 and 406 sharing one or more circuit elements, combined harmonic termination circuit 402 may be smaller and less expensive to manufacture than individual harmonic termination circuits. In some cases, the advantages obtained by sharing circuit elements across multiple harmonic termination circuits may be multiplied for power amplifiers supporting more than two types of operation.

Exemplary class F operation switch harmonic termination circuit

Fig. 5 is a circuit diagram of one example of a switched harmonic termination circuit 500 for class F operation of a power amplifier. Switched harmonic termination circuit 500 includes a harmonic termination circuit 502 and a harmonic termination circuit 504. Harmonic termination circuit 502 may be configured to short circuit the second harmonic of the RF signal. In contrast, the harmonic termination circuit 504 may be configured to present an open circuit impedance to the third harmonic of the RF signal.

Harmonic termination circuit 502 may be formed using inductor L1 and a plurality of switched capacitors, represented by switched capacitor C1. Inductor L1 and switched capacitor C1 may be electrically connected in series. Advantageously, in some embodiments, the harmonic termination circuit 502 may be tuned to support a larger bandwidth than a static harmonic termination circuit by using multiple switched capacitors.

Harmonic termination circuit 504 may include inductor L2 and a plurality of switched capacitors, represented by switched capacitor C2. Inductor L2 and switched capacitor C2 may be electrically connected in parallel. Advantageously, in some embodiments, the harmonic termination circuit 504 may be tuned to support a larger bandwidth than a static harmonic termination circuit by using multiple switched capacitors.

As the frequency of the received signal changes, the configuration of the harmonic termination circuits 502 and 504 may also change. Further, the power amplifier of fig. 5 may support multiple communication bands. For example, as shown in fig. 5, a switch 506 may be used to electrically connect the power amplifier to one of load line 1 or load line 2, which may correspond to communication band a or communication band B, respectively.

Exemplary inverse class F operation switch harmonic termination circuits

Fig. 6 is a circuit diagram of one example of a switched harmonic termination circuit 600 for inverse class F operation of a power amplifier. In certain embodiments, the PA102 may be configured for higher frequencies. In some such cases, it may be difficult to configure the PA102 as a class F amplifier. Thus, in some embodiments, the PA102 may be configured as an inverse class F amplifier. Advantageously, in certain embodiments, the inclusion of the switched harmonic termination circuit 600 enables the PA102 to function as an inverse class F PA 102. Furthermore, as shown with respect to fig. 3 and 4, with the embodiments described herein, a single PA may be used to provide both class F and inverse class F operations. Thus, a wireless device may support two types of operation with one PA instead of two PAs.

Switched harmonic termination circuit 600 includes a harmonic termination circuit 602 and a harmonic termination circuit 604. The harmonic termination circuit 602 may be configured to short circuit the third harmonic of the RF signal. In contrast, the harmonic termination circuit 604 is configured to present an open circuit impedance to the second harmonic of the RF signal. In other words, switching harmonic termination circuit 600 may be configured inversely with switching harmonic termination circuit 500. Further, similar to fig. 5, the power amplifier of fig. 6 may support multiple communication bands.

The harmonic termination circuit 602 may be formed using an inductor L1 and a plurality of switched capacitors, represented by switched capacitor C1. Inductor L1 and switched capacitor C1 may be electrically connected in series. The harmonic termination circuit 604 may include an inductor L2 and a plurality of switched capacitors, represented by switched capacitor C2. Inductor L2 and switched capacitor C2 may be electrically connected in parallel. Advantageously, as with circuits 502 and 504, in some embodiments, harmonic termination circuits 602 and 604 may be tuned to support a larger bandwidth than static harmonic termination circuits by using multiple switched capacitors.

Exemplary class E operating switch harmonic termination circuits

Fig. 7 is a circuit diagram of one example of a switched harmonic termination circuit 700 for class E operation of a power amplifier. Switched harmonic termination circuit 700 includes a harmonic termination circuit 702 and a harmonic termination circuit 704. The harmonic termination circuit 702 may be configured similarly to one of the harmonic termination circuits 502 or 602. Similarly, the harmonic termination circuit 704 may be configured similarly to one of the harmonic termination circuits 504 or 604. In addition, harmonic termination circuits 702 and 704 may each include switches S1 and S2, respectively, that are electrically located between the collector of power amplifier 104 and switched capacitors C1 and C2, respectively. As shown in fig. 7, the design shown in fig. 7 may be used to support a class E power amplifier when switch S1 is closed and switch S2 is open.

In some embodiments, the circuit 700 may also support one or more of class F or inverse class F operation of the power amplifier. The switches S1 and S2 may be opened or closed based on a control signal received from a controller (not shown). By opening S1 and closing S2, the harmonic termination circuits 702 and 704 may be configured as shown in fig. 6 and 7 with respect to the harmonic termination circuits illustrated therein. Thus, by altering the configuration of switches S1 and S2, the power amplifier can be switched to operate as a class F or inverse class F power amplifier. Further, similar to fig. 5 and 6, the power amplifier of fig. 7 may support multiple communication bands, as illustrated by the inclusion of switch 506 and load lines 1 and 2.

Exemplary Power Amplifier Module

Fig. 8 is a block diagram of one example of a power amplifier module 800 that may include the multi-band power amplifier 102. The power amplifier module 800 may include a number of elements. These elements may include, for example, the power amplifier 102 and the controller 806. Each of these power amplifier module elements may be implemented on the same circuit die (die). Alternatively, at least some of the elements of power amplifier module 800 may be implemented on different circuit dies. Advantageously, by implementing the elements on different circuit dies, different semiconductor technologies may be used for different circuit elements of the power amplifier module 800. For example, the PA102 may be implemented using gallium arsenide (GaAs) technology, while the controller 806 may be implemented using silicon (Si).

The power amplifier 102 may include a bias circuit 802 that may bias one or more stages of the power amplifier 102. Biasing one or more stages of the power amplifier 102 may include applying a bias current to transistors of the power amplifier 102.

Further, the power amplifier module 800 may include one or more programmable harmonic termination circuits 804. For example, programmable harmonic termination circuit 804 may include one or more of switched harmonic termination circuits 108, 110, 302, 304, 402, 404, 406, 502, 504, 602, 604, 702, or 704. Selection of the programmable harmonic termination circuit 804 and/or configuration of the selected programmable harmonic termination circuit 804 can be performed by the controller 806.

Controller 806 may include a programmable harmonic termination circuit controller 814, a PA bias controller 810, and a PA class controller 812. PA bias controller 810 may include a controller for selecting bias circuit 802 and/or for controlling the bias current provided by bias circuit 802. The PA bias controller 810 can set the operating point of the PA102 by altering the bias circuit 802.

The PA-class controller 812 may include a controller for selecting a class of operation of the power amplifier 102. Further, the PA class controller 812 may select one or more programmable harmonic termination circuits 804 to electrically connect to the power amplifier 102 based on a selection of a class of the power amplifier 102. For example, if the power amplifier 102 is to operate as a class F power amplifier, the PA-class controller 812 may select the programmable harmonic termination circuits 502 and 504 as the programmable harmonic termination circuit 804 to be in electrical communication with the power amplifier 102.

Programmable harmonic termination circuit controller 814 may include a controller for configuring programmable harmonic termination circuit 804. Configuring the programmable harmonic termination circuit 804 can include opening or closing one or more switches of the programmable harmonic termination circuit 804, thereby electrically connecting one or more capacitors of the programmable harmonic termination circuit 804 to the power amplifier 102. For example, assuming that the programmable harmonic termination circuit 804 includes the combined harmonic termination circuit 402, one or more of the switches S1 through Sn and/or one or more of the switches S1 'through Sn' may be configured by the programmable harmonic termination circuit controller 814.

In some embodiments, the control signals provided by one or more of the controllers 806 may be determined by the manufacturer of the power amplifier module 800 and/or the manufacturer of the wireless device that includes the power amplifier module 800. For example, a manufacturer designing a wireless device to include the power amplifier module 800 functionality and/or use a particular class of power amplifiers within a particular frequency band may program one or more controls into the memory of the wireless device. The controller 806 may access the memory of the wireless device to determine one or more control signals for the power amplifier 102, the bias circuit 802, and/or the programmable harmonic termination circuit 804.

Alternatively or additionally, controller 806 may determine the control signal based at least in part on an operating environment of the wireless device. Further, in some cases, controller 806 may determine the control signal based at least in part on a control and/or request of a base station communicating with the wireless device including power amplifier module 800.

Example Wireless device

Fig. 9 is a block diagram of one example of a wireless device 900 that may include the power amplifier module 800 of fig. 8. Although the wireless device 900 illustrates only one Power Amplifier Module (PAM), in some cases, the wireless device 900 may include multiple PAMs, each of which may or may not have the same configuration as the PAM 800. However, embodiments of the present application enable wireless devices to support operation of multiple amplifier classes and multiple communication bands and technologies using one power amplifier 102. Thus, although some wireless devices 900 may include multiple PAMs 800, in certain embodiments, the wireless device 900 may include a single PAM 800 while supporting multiple communication standards (such as 2G, 3G, 4G, and 4G LTE, etc.). Moreover, it should be understood that wireless device 900 is only one non-limiting example of a wireless device and that other embodiments of wireless device 900 are possible.

In some embodiments, the power amplifier module 800 may be included as part of a larger power amplification system 930, and the power amplification system 930 may be a system on a chip (SoC or SoC). The power amplification system 930 may be part of a transmitter. As shown in fig. 9, the wireless device 900 may include a separate transceiver 904 in electrical communication with a power amplification system 930. However, in other embodiments, the power amplification system 930 may be part of the transceiver 904. In some embodiments, the power amplification system 930 may be part of a Front End Module (FEM).

The power amplification system 930 may include a plurality of switches. For example, the power amplification system 930 may include an antenna switch 916 for transmitting or receiving signals from the antenna 902A across one or more frequency bands. Further, the power amplification system 930 may include a switch 912 for selecting different load lines based on one or more supported communication bands. In addition, switches 912 and 916 may be used to select from among a plurality of duplexers 914A, 914B, 914C, and 914D (which may be collectively referred to as duplexers 914). Duplexer 914 enables bidirectional communication with antenna 902A.

In some cases, the PAM 800 may receive RF signals from the transceiver 904, and the transceiver 904 may be configured and operated in a known manner to generate RF signals to be amplified and transmitted, and to process the received signals. In some embodiments, the PAM 800 is included as part of a transmitter, which may be included in the transceiver 904. In some such cases, the PAM 800 may process the signal for transmission, but not the received signal. In other embodiments, the PAM 800 may process both the received signal and the signal to be transmitted, for example, to a base station.

The transceiver 904 may interact with a baseband subsystem 906, which baseband subsystem 906 is configured to provide conversion between data and/or voice signals suitable for processing by one or more user interface elements and RF signals suitable for processing by the transceiver 904. The transceiver 904 may also be electrically connected to a power management component 922, the power management component 922 configured to manage power for operation of the wireless device. Such power management may also control the operation of the baseband subsystem 906 and the PAM 800, as well as other components. Further, the power management component 922 may provide a supply voltage to a switch mode boost converter (not shown) that may boost the voltage prior to providing the voltage to the PA 102. It should also be understood that power management component 922 may include a power source such as a battery. Alternatively or additionally, the one or more batteries may be a separate component within wireless device 900.

Multiple connections between the various components of wireless device 900 are possible and are omitted from fig. 9 for clarity of illustration only and not to limit the present application. For example, the power management component 922 may be electrically connected to the baseband subsystem 906, the PAM 800, the DSP 924, or other component 926. As a second example, the baseband subsystem 906 may be connected to a user interface processor 908, which may facilitate input and output of voice and/or data provided to and/or received from a user.

The baseband subsystem 906 may also be coupled to memory 910, and the memory 910 may be configured to store data and/or instructions to facilitate operation of the wireless device 900 and/or to provide storage of information to a user. Further, in some embodiments, memory 910 may include an Average Power Tracking (APT) table or other data structure. The APT table may identify a target voltage level for the PA102 that corresponds to a target power level that may be identified by the base station. For example, upon receiving a target power level from a base station, the wireless device may access an APT table to determine a corresponding target voltage level. The target voltage level may be used to set the operating point of the PA 102. Further, the APT table may include different target voltage levels based on the operational class of the PA102 and/or the desired communication band.

In some embodiments, call processor 918 may communicate with a base station. The call processor 918 can interpret commands from the base station and can access the APT table based on commands received from the base station. In addition, the call processor 918 may instruct the PAM 800 to adjust the operating point of the PA 102. Also, the call processor 918 can instruct the controller 806 to configure the PA102 to operate in a particular class, such as class E, class J, class F, or inverse class F. Configuring operation of the PA102 may include configuring the programmable harmonic termination circuit 804. In addition, the call processor 918 can instruct the controller 806 to configure the PA102 to process signals within a particular frequency band.

In addition to the foregoing, wireless device 900 may also include one or more central processors 920. Each central processor 920 may include one or more processor cores. Further, wireless device 900 may include one or more antennas 902A, 902B. In some cases, one or more antennas in wireless device 400 may be configured to transmit and/or receive at different frequencies or within different frequency ranges. Further, one or more antennas may be configured to operate in different wireless networks. Thus, for example, antenna 902A may be configured to transmit and receive signals over a 2G network and antenna 902B may be configured to transmit and receive signals over a 3G or 4G LTE network. In some cases, antennas 902A and 902B may both be configured to transmit and receive signals, for example, over a 2.5G network, but at different frequencies.

In some embodiments, each antenna may be in electrical communication with the PAM 800 and/or the power amplification system 930. Alternatively or additionally, each antenna may be associated with or in electrical communication with a different PAM or power amplification system. Thus, while antenna 902A is in electrical communication with power amplification system 930, antenna 902B may be in electrical communication with another power amplification system (not shown). Moreover, in some embodiments, antenna 902A may be a primary antenna (primary antenna) and antenna 902B may be a diversity antenna, or vice versa.

A number of other wireless device configurations may utilize one or more of the features described herein. For example, the wireless device need not be a multi-band device. In another example, the wireless device may include additional antennas, such as diversity antennas, and additional connectivity features, such as Wi-Fi, bluetooth, and GPS. Further, the wireless device 900 may include any number of additional components 926, such as analog-to-digital converters, digital-to-analog converters, graphics processing units, solid state drives, and so forth. Moreover, the wireless device 900 may include any type of device that may communicate over one or more wireless networks and may include the PA102 and/or the PAM 800. For example, wireless device 900 may be a cellular phone, including a smart phone or a non-smart phone (dumbphone), a tablet, a laptop, a video game device, a smart appliance, or the like.

Exemplary Power Amplifier class selection processing

Fig. 10 is a flow diagram of one example of a power amplifier class selection process 1000. It should be appreciated that process 1000 is one example of a process for selecting and/or configuring a class of operation for a power amplifier, such as power amplifier 102. Other processes for selecting and/or configuring operational classes of power amplifiers are also possible. For example, the operations of process 1000 may be performed in a different order or substantially in parallel. Thus, the order of the operations described with respect to process 1000 is for ease of description and not limiting of process 1000. Also, it is understood that various systems including various hardware, software, firmware, or combinations thereof, may implement at least some portions of process 1000. For example, process 1000 may be performed, at least in part, by controller 806, programmable harmonic termination circuit controller 814, PA bias controller 810, PA class controller 812, various combinations of the above, and the like. To simplify the discussion and not to limit the application, process 1000 will be described with respect to a particular system.

In block 1002, the process 1000 may begin, for example, when the PA-class controller 812 receives a PA-class control signal. The PA-type control signals may be received from call processor 918 and/or may be accessed from memory 910. Alternatively, the PA-class controller 812 may generate PA-class control signals based at least in part on information or configuration data accessed from the memory 910, received from the call processor 918, or received from a base station. In some cases, the PA-class control signal may include configuration information provided by the manufacturer of wireless device 900 and/or from a base station.

In block 1004, the PA class controller 812 identifies a PA class based at least in part on the PA class control signal received in block 1002. In block 1006, the PA class controller 812 connects the second harmonic notch filter associated with the PA class identified in block 1004 to the output stage 104 of the power amplifier 102. In some embodiments, the second harmonic notch filter may be one of a plurality of second harmonic notch filters. At least some of the plurality of second harmonic notch filters may be associated with different operational classes of the power amplifier 102. For example, one second harmonic notch filter may be associated with a class F power amplifier and another second harmonic notch filter may be associated with an inverse class F power amplifier.

In block 1008, the PA class controller 812 disconnects the remaining second harmonic notch filter from the output stage 104 of the power amplifier 102. In some embodiments, block 1008 may be optional or omitted. For example, block 1008 is omitted in the event that the remaining harmonic notch filters have been disconnected from the power amplifier 102.

In block 1010, the PA class controller 812 connects the third harmonic notch filter associated with the PA class identified in block 1004 to the output stage 104 of the power amplifier 102. In some embodiments, the third harmonic notch filter may be one of a plurality of third harmonic notch filters. At least some of the plurality of third harmonic notch filters may be associated with different operational classes of the power amplifier 102. For example, one third harmonic notch filter may be associated with a class F power amplifier and another third harmonic notch filter may be associated with a class E power amplifier.

In block 1012, the PA-class controller 812 disconnects the remaining third harmonic notch filter from the output stage 104 of the power amplifier 102. In some embodiments, block 1012 may be optional or omitted. For example, block 1012 is omitted in the event that the remaining harmonic notch filters have been disconnected from the power amplifier 102.

The function of the harmonic notch filters connected in blocks 1006 and 1010 may depend on the type of class of the power amplifier 102. In some cases, the second harmonic notch filter connected in block 1006 may exhibit a short circuit for the second harmonic frequency or the 2F0 frequency. Further, in some such cases, the third harmonic notch filter connected in block 1010 may present an open circuit impedance for the third harmonic frequency or the 3F0 frequency. For example, as shown in fig. 5, a class F amplifier may include such a configuration. In other cases, the second harmonic notch filter connected in block 1006 may present an open circuit impedance for the second harmonic frequency or the 2F0 frequency. Further, in some such cases, the third harmonic trap connected in block 1010 may exhibit a short circuit for the third harmonic frequency or the 3F0 frequency. For example, as shown in fig. 5, an inverse class F amplifier may include such a configuration.

In some embodiments, a harmonic notch filter may be connected to the output stage 104 of the power amplifier 102 for additional harmonics of the received signal, such as the fourth harmonic, the fifth harmonic, and so on. In other cases, however, the harmonic notch filter is used only for the second or third harmonic of the received signal.

In some embodiments, additional harmonic notch filters may be included as interstage switch harmonic terminations 110. As shown, for example, in fig. 1, an additional inter-stage switch harmonic terminal 110 may be in electrical communication with the base of the output transistor 104. Typically, an inter-stage harmonic notch filter is not included as part of the additional stages of the power amplifier 102 because, in general, the gain of the received signal is too small to substantially benefit from including an inter-stage harmonic notch filter at an earlier stage of the power amplifier 102. However, in some embodiments, additional inter-stage harmonic notch filters may be included as part of the power amplifier 102. For example, in a three stage power amplifier, an inter-stage harmonic notch filter may be included before the output stage and before the second to last transistor stage.

In block 1014, the programmable harmonic termination circuit controller 814 identifies the operating frequency for the power amplifier class. The programmable harmonic termination circuit controller 814 may determine the operating frequency by accessing a manufacturer program in the memory 910 for control. Typically, the operating frequency of a particular PA class is static and is based on the manufacturer specifications of wireless device 900. However, in some cases, the operating frequency may be dynamic. For example, in some cases, the operating frequency may be different based on distance from the base station and/or commands from the base station.

In block 1016, the programmable harmonic termination circuit controller 814 configures one or more switches of a second harmonic notch filter based at least in part on the operating frequency identified in block 1014. By configuring one or more switches of the second harmonic notch filter, one or more capacitors of the harmonic notch filter may be electrically connected to the collector of the output stage 104 of the power amplifier 102. Further, in some cases, one or more capacitors of the second harmonic inter-stage harmonic notch filter may be electrically connected to the base of the output stage 104 of the power amplifier 102.

In block 1018, the programmable harmonic termination circuit controller 814 configures one or more switches of a third harmonic notch filter based at least in part on the operating frequency identified in block 1014. By configuring one or more switches of the third harmonic notch filter, one or more capacitors of the harmonic notch filter may be electrically connected to the collector of the output stage 104 of the power amplifier 102. Further, in some cases, one or more capacitors of the third harmonic inter-stage harmonic notch filter may be electrically connected to the base of the output stage 104 of the power amplifier 102.

In block 1020, the controller 806 modifies the output impedance matching network 112 based at least in part on the PA class and the fundamental operating frequency. The fundamental operating frequency may correspond to a harmonic frequency handled by a harmonic notch filter. In some cases, the PA102 is a high impedance power amplifier. Thus, in some cases, a smaller impedance transformer is required compared to other power amplifier designs. Also, in some cases, an impedance transformer is not necessary. Thus, in some cases, the output impedance matching network 112 may be omitted. Thus, in some cases, block 1020 may be optional or omitted. In some such cases, the power amplifier 102 may be electrically connected to a low pass filter.

In certain embodiments, the process 1000 may be used to alter one or more of the operating class of the PA102 and the operating frequency of the PA 102. Thus, in certain embodiments, the embodiments described herein enable dynamic operation of the wireless device 900 and the PA 102. Often, the operating class and operating frequency of the PA102 will be static during a particular call or during a particular communication time slot with a base station. However, in some cases, the PA102 may be reconfigured during the call. For example, during handoff between base stations, the PA102 may be reconfigured to support different classes and/or frequencies.

Term(s) for

Unless the context clearly requires otherwise, throughout the description and the claims, the terms "comprise", "comprising" and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, that is, in the sense of "including but not limited to". The term "coupled" is used to indicate a connection between two elements and refers to two or more elements that may be connected directly or by way of one or more intermediate elements. Further, as used in this application, the terms "herein," "above," "below," and terms of similar import shall refer to this application as a whole and not to any particular portions of this application. Terms in the above detailed description using the singular or plural number may also include the plural or singular number, respectively, as the context permits. The term "or" when referring to a list of two or more items, this term covers all of the following interpretations of the term: any of the items in the list, all of the items in the list, and any combination of the items in the list.

The above detailed description of embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise form disclosed above. While specific embodiments of, and examples for, the invention are described above for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. For example, while processes or blocks are presented in a given order, alternative embodiments may perform processes having steps in a different order, or employ systems having blocks in a different order, and some processes or blocks may be deleted, moved, added, subtracted, combined, and/or modified. Each of these processes or blocks may be implemented in a variety of different ways. Likewise, while processes or blocks are sometimes shown as being performed in series, these processes or blocks may instead be performed in parallel, or may be performed at different times.

The teachings of the invention provided herein can be applied to other systems, not necessarily the systems described above. The elements and acts of the various embodiments described above can be combined to provide further embodiments.

Conditional language, such as "may," "might," "meeting," "e.g.," and the like, as used herein, is generally intended to indicate that certain embodiments include, but not necessarily include, certain features, elements and/or states, unless specifically stated otherwise, or otherwise understood in the context as used. Thus, such conditional language is not generally intended to imply that features, elements, and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for determining, with or without designer input or prompting, whether such features, elements, and/or states are included or are to be performed in any particular embodiment.

Unless specifically stated otherwise, or otherwise understood in the context as used, a disjunctive language such as the phrase "X, Y or at least one of Z" is generally used to present an item, entry, etc. that may be X, Y or Z, or any combination thereof (e.g., X, Y and/or Z). Thus, such disjunctive language is generally not intended to, and should not, imply that certain embodiments require the presentation of each of at least one of X, at least one of Y, or at least one of Z.

Articles such as "a" or "an" should generally be construed to include one or more of the described items unless expressly stated otherwise. Accordingly, a phrase such as "an apparatus configured to" is intended to include the one or more recited apparatuses. Such one or more recited devices may also be collectively configured to perform the illustrated narration (recitations). For example, "a processor configured to execute statements A, B and C" may include a first processor configured to execute statement a, which is configured to work in conjunction with a second processor that executes statements B and C.

While certain embodiments of the present invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the application. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the application. The drawings and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the application.

Claims (20)

1. A method of operating a power amplifier, comprising:

obtaining a power amplifier class control signal associated with a power amplifier, the power amplifier comprising a first stage and a second stage;

connecting a second harmonic notch filter associated with a power amplifier class associated with the power amplifier class control signal to a second stage of the power amplifier, the second harmonic notch filter located between the first stage and the second stage;

identifying an operating frequency for the power amplifier class;

configuring one or more switches of the second harmonic notch filter based at least in part on the identified operating frequency; and

altering an output impedance matching network based at least in part on the power amplifier class and the identified operating frequency.

2. The method of claim 1, further comprising identifying the power amplifier class based at least in part on the obtained power amplifier class control signal.

3. The method of claim 1, further comprising disconnecting all other second harmonic notch filters except the connected second harmonic notch filter.

4. The method of claim 1, further comprising connecting a third harmonic notch filter associated with the power amplifier class control signal to a second stage of the power amplifier.

5. The method of claim 4, further comprising disconnecting all other third harmonic notch filters except the connected third harmonic notch filter.

6. The method of claim 4, further comprising configuring one or more switches of the third harmonic notch filter based at least in part on the identified operating frequency.

7. The method of claim 6, further comprising:

in response to identifying class F operation based at least in part on the obtained power amplifier class control signal:

altering a configuration of one or more switches of the second harmonic notch filter to short circuit a second harmonic frequency of the power amplifier class control signal; and

altering a configuration of one or more switches of the third harmonic notch filter to present an open circuit impedance to a third harmonic frequency of the power amplifier class control signal.

8. The method of claim 6, further comprising:

in response to identifying an inverse class F operation based at least in part on the obtained power amplifier class control signal:

altering a configuration of one or more switches of the second harmonic notch filter to present an open circuit impedance to a second harmonic frequency of the power amplifier class control signal; and

altering a configuration of one or more switches of the third harmonic notch filter to short circuit a third harmonic frequency of the power amplifier class control signal.

9. A power amplifier module comprising:

a multi-stage power amplifier comprising at least a first stage and a second stage, the multi-stage power amplifier configured to receive a signal;

an inter-stage programmable harmonic termination circuit located between the first stage and the second stage, the inter-stage programmable harmonic termination circuit comprising a plurality of switches and an inductor connected to at least one switch of the plurality of switches; and

a controller configured to alter a configuration of the plurality of switches of the inter-stage programmable harmonic termination circuit based at least in part on a harmonic frequency of the signal.

10. The power amplifier module of claim 9 wherein the second stage is an output stage of the power amplifier.

11. The power amplifier module of claim 9 wherein the harmonic frequency of the signal is one of a second harmonic frequency or a third harmonic frequency.

12. The power amplifier module of claim 11 wherein the controller is further configured to alter the configuration of the plurality of switches with respect to one of the second harmonic frequency or the third harmonic frequency based at least in part on a particular class of operation of the multi-stage power amplifier.

13. The power amplifier module of claim 12 wherein the particular class of operation of the multi-stage power amplifier corresponds to a communication frequency band from a plurality of communication frequency bands supported by the multi-stage power amplifier.

14. The power amplifier module of claim 9 further comprising an output stage programmable harmonic termination circuit located after and in electrical communication with the second stage.

15. The power amplifier module of claim 14 wherein the output stage programmable harmonic termination circuit supports a plurality of operational classes of the multi-stage power amplifier.

16. A wireless device, comprising:

a plurality of load lines, at least some of the load lines corresponding to different communication frequency bands;

a switch network configured to electrically connect a load line of the plurality of load lines to a power amplifier; and

a power amplifier module comprising a multi-stage power amplifier comprising at least a first stage and a second stage and configured to receive a signal, an inter-stage programmable harmonic termination circuit located between the first stage and the second stage and comprising a plurality of switches, and a controller configured to alter a configuration of the plurality of switches of the inter-stage programmable harmonic termination circuit based at least in part on a harmonic frequency of the signal.

17. The wireless device of claim 16, wherein the second stage is an output stage of the multi-stage power amplifier.

18. The wireless device of claim 16, wherein the harmonic frequency of the signal is one of a second harmonic frequency or a third harmonic frequency.

19. The wireless apparatus of claim 18, wherein the controller is further configured to alter a configuration of the plurality of switches with respect to one of the second harmonic frequency or the third harmonic frequency based at least in part on a particular class of operation of the multi-stage power amplifier.

20. The wireless device of claim 16, wherein the power amplifier module further comprises a programmable harmonic termination circuit in electrical communication with an output of the second stage.