KR102381231B1 - Rf transceiver front end module with improved linearity - Google Patents

Abstract

The power amplifier system front end measures both forward and reverse power associated with an RF transmit signal. The processor is configured to use measurements derived from the measured forward and reverse power output to adjust the RF transmit signal to compensate for one or more memory effects of the power amplifier system.

Description

RF TRANSCEIVER FRONT END MODULE WITH IMPROVED LINEARITY

Any priority applications are incorporated by reference

If necessary, any and all applications for which foreign or domestic priority claims are identified in the application data sheet of this application are hereby incorporated by reference under 37 CFR 1.57.

Field

FIELD OF THE INVENTION Embodiments of the present invention relate to electronic systems, and more particularly to systems comprising power amplifiers for radio frequency (RF) electronic devices.

Power amplifiers may be included in mobile devices to amplify an RF signal for transmission via an antenna. For example, Global System for Mobile Communications (GSM), code division multiple access (CDMA), and wideband code division multiple access (W-CDMA) In mobile devices having a time division multiple access (TDMA) architecture, such as those found in systems, a power amplifier may be used to amplify an RF signal with relatively low power. Power amplifiers may also be included in mobile device front end modules including duplexers, antenna switch modules, and couplers. Existing front-end modules may experience significant performance degradation under certain circumstances, including degraded linearity.

Embodiments are described herein to address these and other problems. For example, degraded linearity can be observed across multiple frequency bands and in multiple modes, such as average power tracking (APT) mode, envelope tracking (ET) mode, digital predistortion ( may be of particular importance for front end modules operating in one or more of a digital pre-distortion (DPD) mode (eg, fixed supply or ET DPD modes), and the like. One problem is degraded linearity (eg, adjacent channel leakage ratio [ACLR]) when a mismatch is presented to the antenna. This may be particularly the case under ET DPD mode when the power amplifier is driven with a wideband signal such as a 50 resource block long term evolution signal (50 RB LTE). In such a case, a drop of 10 Decibels (dB) may exist when, for example, a 5:1 voltage standing wave ratio (VSWR) is provided to the antenna. Such degradation can be progressively exacerbated when the modulation bandwidth is increased. Thus, it can be particularly beneficial to compensate for this degradation under ET and high modulation bandwidth cases.

The performance degradation can be exacerbated by the duplexer, for example when the system is in ET mode. For example, the group delay inherent in the duplexer combined with a bad match can cause memory effects, for example the system gain shape (eg AM-AM/AM-PM) may depend on the transmitted RB bandwidth (ie , across the channel). Moreover, AM-AM (amplitude vs. amplitude) and/or AM/PM (amplitude vs. phase) response changes may occur over various mismatch conditions (even for narrowband signals) due to PA compression point change through mismatch. often experienced A typical open loop, memoryless DPD is often insufficient to handle gain shape changes within the transmitted bandwidth. Accordingly, certain embodiments disclosed herein adjust the DPD for the memory, as well as certain mismatch conditions at the antenna, and otherwise address the memory (ie gain shape changes across the channel). In addition, the appropriate (eg, optimal) delay applied between the modulator and the RF signal (for ET operation) is also a function of the VSWR state and varies within the TX channel. Accordingly, certain embodiments described herein also adapt such delays within the transmitted bandwidth.

According to certain aspects of the present disclosure, systems and methods are provided for improving mobile device front end module performance (eg, linearity) through mismatch. This can be achieved without incurring significant additional loss of performance under nominal conditions. Depending on the particular implementation, embodiments provided herein may provide such gains in ET mode, APT mode, DPD mode, or combinations thereof, such as combined DPD/ET mode.

A power amplifier system is provided in accordance with at least one aspect of the present disclosure. The system includes a modulator configured to generate a radio frequency (RF) transmit signal and a front end module. The front end module may include a power amplifier configured to amplify the RF transmit signal to generate an amplified RF transmit signal. The front end module may also include a coupler positioned between the antenna and the power amplifier. The coupler may be configured to output a measure of both forward and reverse power associated with the RF transmit signal. The coupler is a dual directional coupler in some embodiments. The system may additionally include a non-volatile memory that stores an equalizer table. The equalizer table may have a plurality of entries generated during pre-characterization of the front end module. The system also receives (a) voltage standing wave ratio (VSWR) measurements derived from forward and reverse power output by the coupler, (b) accesses entries in the equalizer table based at least in part on the VSWR measurements, and , (c) a processor configured to adjust the RF transmit signal based on the accessed entries to compensate for one or more memory effects present in the power amplifier system. For example, the system may include a digital predistortion table (DPD), wherein the processor is configured to adjust the RF transmission signal by adapting values in the DPD table based on accessed entries in the equalizer table. The system may be in the form of a mobile device, which may further include an antenna configured to receive the amplified RF signal from the front end module.

The front end module of the power amplifier system can be configured in several different ways. The equalizer table is, in some cases, generated using a programmable antenna tuner to tune the front end module to the desired VSWR points. In some situations, the front end module does not include an integrated antenna tuner. A programmable antenna tuner may be included in the front end module and positioned between the antenna and the coupler in some implementations. The programmable antenna tuner may be adjustable to tune the impedance seen by the power amplifier to provide coarse correction of nonlinearities within the power amplifier system. Adjustment of the RF transmit signal based on accessed entries can provide fine correction of nonlinearities within the power amplifier system. The front end module may include one or more duplexers positioned between the power amplifier and the dual directional coupler. In some cases, duplexers contribute to at least some of the memory effects.

The power amplifier system may further include an envelope tracking system configured to provide a power supply control signal to the power amplifier to control a voltage level of the power amplifier based on the shaped envelope signal. The processor is, in some cases, further configured to adjust the delay between the RF transmit signal and the supply control signal based on delay values included in the accessed equalizer table entries.

A method of characterizing a front end module of a wireless device is provided in accordance with additional aspects of the present disclosure. The method includes using a programmable antenna tuner to tune an impedance load at an output of a power amplifier of a front end module to achieve a voltage standing wave ratio (VSWR) value associated with a first characterization state of a plurality of front end module characterization states. may include steps. The method may also include driving the front end module with the RF transmit signal. The RF transmit signal may be driven according to one or more additional parameter values associated with the first characterization state. The method may further include measuring one or more variables associated with a behavior of the front end module while the front end module is driven by the RF transmit signal and tuned to VSWR values. The one or more recorded variables may include power amplifier compression, maximum envelope power, and/or a delay between the power control signal and the RF transmit signal for the power amplifier. The method may also include recording the one or more measured variables in association with the first characterization state in a table in the non-volatile memory. The steps of using, running, measuring, and recording may be repeated for a plurality of additional characterization states of the plurality of front end module characterization states. The programmable antenna tuner is in some cases separate from the front end module, the front end module not including the antenna tuner. A programmable antenna tuner is integrated into the front end module in some other implementations.

A power amplifier system in accordance with still other aspects includes a front end module including a power amplifier configured to amplify an RF transmit signal to generate an amplified RF transmit signal. The front end module may also include a programmable antenna tuner coupled to the antenna. A coupler of the front end module may be positioned between the power amplifier and the antenna tuner, wherein the coupler is configured to output a measure of both forward and reverse power associated with the RF signal. The antenna tuner may be adjustable to tune the impedance seen by the power amplifier to provide approximate correction of nonlinearities within the power amplifier system. The system may further include a non-volatile memory for storing an equalizer table having a plurality of entries generated during precharacterization of the front end module. The system also (a) receives voltage standing wave ratio (VSWR) measurements derived from forward and reverse power output by the coupler, (b) accesses entries in the equalizer table based at least in part on the VSWR, ( c) a processor configured to adjust the RF transmission signal based on the accessed entries. The front end module may additionally include a duplexer in some configurations.

1 is a schematic diagram of a power amplifier module for amplifying a radio frequency (RF) signal;
2 is a schematic block diagram of an example wireless device.
3 is a schematic block diagram of an example of a power amplifier system including a transceiver and a front end module in accordance with certain embodiments.
4A is a schematic diagram of one embodiment of a front end module without an integrated antenna tuner;
4B is a schematic diagram of one embodiment of a front end module with an integrated programmable antenna tuner;
5 is a flow diagram illustrating a process for precharacterizing a front end module.
6A-6B show examples of partial equalizer lookup tables for an exemplary front-end module representing pre-characterized values for select variables at different characterization states.
7A shows a flow diagram depicting a process for compensating for front end module operation using an equalizer lookup table.
7B shows a flow diagram depicting another process for compensating for front end module operation through the combined use of coarse tuning by an integrated antenna tuner and fine tuning using an equalizer lookup table.
8A-8C show power amplifier signal and supply waveforms for power amplifiers operating in fixed supply voltage mode, average power tracking mode, and envelope tracking mode, respectively.
9 shows an embodiment of a process for determining a complex impedance.

The headings provided herein, where necessary, are for convenience only and do not necessarily affect the scope or meaning of the claimed invention.

1 is a schematic diagram of a power amplifier module (PAM) 10 for amplifying a radio frequency (RF) signal. The illustrated power amplifier module 10 may be configured to amplify the RF signal RF_IN to generate the amplified RF signal RF_OUT. As described herein, the power amplifier module 10 may include one or more power amplifiers.

2 is a schematic block diagram of an exemplary wireless device 11 that may include one or more of the power amplifier modules 10 of FIG. 1 . The wireless device 11 may include power amplifiers 17 and an RF front end 12 implementing one or more features of the present disclosure. For example, power amplifiers 17 and RF front end 12 in accordance with some embodiments may include those caused by memory effects resulting from an impedance mismatch seen by power amplifiers 17 . , is configured to compensate for nonlinearities. In particular, the duplexers coupled to the output power amplifiers 17 may include or act as filters that add corresponding frequency response components to the system in addition to other distortion, creating memory effects. For example, duplexers may provide a non-flat mismatch across the transmit channel/band, resulting in non-linear power amplifier behavior.

Such compensation may involve the use of a lookup table or other data structure, suitable lookup table entries being taken during operation, such as the voltage standing wave ratio (VSWR) to complex impedance seen by the power amplifiers 17 . Accessed based on measurements or other measurements. Values in a lookup table according to specific implementations are obtained during the characterization phase, and a programmable antenna tuner is used to record specific variables characterizing the behavior of the system. For example, AM-AM and/or AM-PM response curves for power amplifier 17 may be captured over various operating states. Such techniques and associated components will be described in greater detail herein.

Although the power amplifiers 17 and RF front end 12 are described as separate components in some cases, some or all of the power amplifiers 17 may also include, for example, the RF front end 12 as power amplifiers ( 17) may form part of the RF front end 12 in embodiments that are highly integrated components. The combination of power amplifiers 17 and RF front end 12 may together be referred to as a front end module.

The example wireless device 11 shown in FIG. 2 may represent a multi-band and/or multi-mode device such as a multi-band/multi-mode mobile phone. As examples, the Mobile Communication System (GSM) standard is a mode of digital cellular communication used in many parts of the world. GSM mode mobile phones may operate in one or more of four frequency bands: 850 MHz (approximately 824-849 MHz for Tx, 869-894 MHz for Rx), 900 MHz (approximately 880-915 for Tx) MHz, 925 to 960 MHz for Rx), 1800 MHz (approximately 1710 to 1785 MHz for Tx, 1805 to 1880 MHz for Rx), and 1900 MHz (approximately 1850 to 1910 MHz for Tx, 1930 to Rx) 1990 MHz). Variations of GSM bands and/or local/national implementations are also used in different parts of the world.

Code Division Multiple Access (CDMA) is another standard that may be implemented in mobile phone devices. In certain implementations, CDMA devices may operate in one or more of the 800 MHz, 900 MHz, 1800 MHz and 1900 MHz bands, while certain W-CDMA and Long Term Evolution (LTE) devices are For example, it may operate over approximately 22 radio frequency spectrum bands.

One or more features of the disclosure may be implemented in the exemplary modes and/or bands described above, and other communication standards. For example, 3G and 4G are non-limiting examples of such standards.

The illustrated wireless device 11 includes an RF front end 12 , a transceiver 13 , an antenna 14 , power amplifiers 17 , a control component 18 , a computer readable medium 19 , a processor 20 . ), a battery 21 , and a supply control block 22 .

The transceiver 13 may generate RF signals for transmission via the antenna 14 . Moreover, the transceiver 13 may receive incoming RF signals from the antenna 14 .

It will be appreciated that various functionalities associated with the transmission and reception of RF signals may be achieved by one or more components collectively represented in FIG. 2 as transceiver 13 . For example, a single component may be configured to provide both transmit and receive functionalities. In another example, transmit and receive functionalities may be provided by separate components.

Similarly, it will be appreciated that various antenna functionalities associated with the transmission and reception of RF signals may be achieved by one or more components collectively represented in FIG. 2 as antenna 14 . For example, a single antenna may be configured to provide both transmit and receive functionalities. In another example, transmit and receive functionalities may be provided by separate antennas. In another example, different antennas may be provided in different bands associated with the wireless device 11 .

2 , one or more output signals from a transceiver 13 are shown to be provided to an antenna 14 via one or more transmit paths 15 . In the example shown, different transmit paths 15 may represent output paths associated with different bands and/or different power outputs. For example, the two exemplary power amplifiers 17 shown may include amplifiers associated with different power output configurations (eg, low power output and high power output), and/or associated with different bands. Amplifications can be expressed. 2 illustrates the wireless device 11 as including two transmission paths 15 , the wireless device 11 may be adapted to include more or fewer transmission paths 15 .

2 , one or more detected signals from antenna 14 are shown being provided to transceiver 13 via one or more receive paths 16 . In the example shown, different receive paths 16 may represent paths associated with different bands. For example, the four example paths 16 shown may represent the quad band capability provided in some wireless devices. 2 illustrates the wireless device 11 as including four receive paths 16 , the wireless device 11 may be adapted to include more or fewer receive paths 16 .

To facilitate switching between the receive and transmit paths, one or more switches within the RF front end 12 may be configured to electrically couple the antenna 14 to a selected transmit or receive path. Accordingly, the switches may provide a number of switching functionalities associated with the operation of the wireless device 11 . In certain embodiments, the switches are multiple configured to provide functionalities associated with, for example, switching between different bands, switching between different power modes, switching between transmit and receive modes, or some combination thereof. may include switches of The switches may also be configured to provide additional functionality, including filtering and/or duplexing of signals.

2 illustrates various control functionalities associated with the operations of the RF front end, power amplifiers 17, supply control 22, and/or other operating components in which control component 18, in certain embodiments, may be configured. It shows what can be provided to control. The control component 18 may in some cases be included, for example, within another component shown in FIG. 2 , such as the transceiver 13 .

In certain embodiments, the processor 20 may be configured to facilitate implementation of the various processes described herein. In certain implementations, the processor 20 may operate using computer program instructions. In certain embodiments, such computer program instructions may also be stored in computer readable memory 19 which may instruct a computer or other programmable data processing device to operate in a particular manner. For example, for purposes of explanation, embodiments of the present disclosure may also be described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, may be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing device to create a machine, such that the instructions for execution by the processor of the computer or other programmable data processing device are flow diagrams. and/or the block diagram creates a means for implementing the block or actions assigned to the blocks.

In certain embodiments, such computer program instructions may also be stored in computer readable memory 19 that may instruct a computer or other programmable data processing device to operate in a particular manner, such that the computer readable memory The instructions create an article of manufacture comprising instruction means for implementing the acts specified in the flowchart and/or block diagram block or blocks. Computer program instructions may also be loaded into a computer or other programmable data processing device to cause a series of operations to be performed on the computer or other programmable device to create a computer implemented process, such that the instructions execute on the computer or other programmable device. The flowcharts and/or block diagrams provide steps for implementing the acts specified in the block or blocks.

The supply control block 22 may be electrically coupled to the battery 21 , and the supply control block 22 is configured to change the voltage provided to the power amplifiers 17 based, for example, on the envelope of the RF signal being amplified. can be configured. Battery 21 may be any suitable battery for use in wireless device 11 , including, for example, a lithium ion battery. As will be described in more detail below, by controlling the voltage level of the power amplifier supply voltage provided to the power amplifiers, the power consumption of the battery 21 can be reduced, thereby improving the performance of the wireless device 11 . do. As illustrated in FIG. 2 , the envelope signal may be provided from the transceiver 13 to the supply control block 22 . However, the envelope may be determined in other ways. For example, the envelope or other type of supply control signal may be determined by processing the RF signal (eg, detecting the envelope using any suitable envelope detector).

One technique for reducing the power consumption of a power amplifier is envelope tracking (ET), in which the voltage level of the power supply of the power amplifier is changed with respect to the envelope of the RF signal. For example, when the envelope of the RF signal increases, the voltage level of the power supply of the power amplifier may increase. Likewise, when the envelope of the RF signal decreases, the voltage level of the power supply of the power amplifier may be decreased to reduce power consumption. Another form of power tracking is average power tracking (APT), in which the voltage level of the power supply of the power amplifier 17 is changed with respect to the envelope, similar to envelope tracking. However, in the APT mode of operation, the power supply is varied between two or more distinct values based on the average level of the envelope. For example, the power level may be changed per slot, with each slot corresponding to a different power control level. This may improve efficiency at low power while causing fewer power savings at higher levels than ET tracking. Another mode of power supply control is a fixed supply or direct battery connection, wherein the power supply to the power amplifier 17 is maintained at a fixed amount, at or above the maximum level of the envelope of the RF signal. Example power and signal waveforms generated during example fixed power supply, average power tracking, and envelope tracking operations are shown in FIGS. 8A, 8B, and 8C , respectively.

3 is a schematic block diagram of an example of a power amplifier system 26 . For example, the power amplifier system 26 may be integrated into the wireless device 11 . The illustrated power amplifier system 26 includes an RF front end 12 , an antenna 14 , a battery 21 , a supply control driver 30 , a power amplifier 17 , and a transceiver 13 . The illustrated transceiver 13 is a baseband processor 34 , a supply forming block or circuit 35 , a delay component 33 , a digital-to-analog converter (DAC) 36 , a quadrature an (I/Q) modulator 37 , a mixer 38 , and an analog-to-digital converter (ADC) 39 . Feed shaping block 35 , delay component 33 , DAC 36 , and feed control driver 30 together form feed shaping branch 48 .

The baseband processor 34 may be used to generate I and Q signals corresponding to signal components of a sine wave or a signal of a desired amplitude, frequency, and phase. For example, an I signal may be used to represent the in-phase component of a sine wave and a Q signal may be used to represent a quadrature component of a sine wave, which may be an equivalent representation of the sine wave. In certain implementations, the I and Q signals may be provided to the I/Q modulator 37 in digital format. Baseband processor 34 may be any suitable processor configured to process baseband signals. For example, the baseband processor 34 may include a digital signal processor, a microprocessor, a programmable core, or any combination thereof. Moreover, in some implementations, two or more baseband processors 34 may be included in power amplifier system 26 .

I/Q modulator 37 may be configured to receive I and Q signals from baseband processor 34 and process the I and Q signals to generate an RF signal. For example, I/Q modulator 37 converts DACs configured to convert I and Q signals to analog format, mixers to upconvert I and Q signals to radio frequency, and upconverted I and Q signals. It may include a signal combiner for combining into an RF signal suitable for amplification by the power amplifier 17 . In certain implementations, I/Q modulator 37 may include one or more filters configured to filter the frequency component of signals processed therein.

The supply shaping block 35 converts an envelope or amplitude signal associated with the I and Q signals into a shaped power supply control signal, such as an average power tracking (APT) signal or an envelope tracking (ET) signal, according to an embodiment. can be used for Shaping the envelope signal from the baseband processor 34 may help increase the performance of the power amplifier system 26 . In certain implementations, such as where the feed shaping block is configured to implement an envelope tracking function, the feed shaping block 35 is a digital circuit configured to generate a digital shaped envelope signal, and the DAC 36 is a digital shaping It is used to convert the converted envelope signal into an analog shaped envelope signal suitable for use by the supply control driver 30 . However, in other implementations, DAC 36 may advantageously be omitted to provide a digital envelope signal to supply control driver 30 to assist supply control driver 30 in further processing of the envelope signal.

The supply control driver 30 may receive a supply control signal (eg, an analog shaped envelope signal or an APT signal) from the transceiver 13 and receive a battery voltage V _BATT from the battery 21 , and transmit The supply control signal may be used to generate a power amplifier supply voltage V _{CC _PA} for the power amplifier 17 that is varied with respect to the signal. The power amplifier 17 may receive the RF transmit signal from the I/Q modulator 37 of the transceiver 13 , and may provide the amplified RF signal to the antenna 14 via the RF front end 12 . . In other cases, the fixed power amplifier supply voltage V _{CC _PA} is provided to the power amplifier 17 . In some such embodiments, one or more of the feed shaping block 35 , the DAC 36 , and the feed control driver 30 may not be included. Example waveforms of the power amplifier supply voltage V _{CC _PA} and corresponding RF transmit signals are shown in FIGS. 8A , 8B , and 8C for fixed supply, APT, and ET power supply control operations, respectively. In some embodiments, power amplifier system 26 may perform two or more supply control techniques. For example, power amplifier system 26 allows selection (eg, via firmware programming or other suitable mechanism) for two or more of ET, APT, and fixed power supply control modes. In such cases, the baseband processor or other suitable controller or processor may instruct supply shaping block 35 to enter the appropriate select mode.

The delay component 33 implements a selectable delay in the supply control path. As will be described in more detail, this may be useful in some cases to compensate for nonlinearities and/or other potential sources of signal degradation. The illustrated delay component is shown in the digital domain as part of the transceiver 13 and may include a FIFO or other type of memory based delay component. However, delay component 33 may be implemented in any suitable manner, for example, and may be incorporated as part of feed forming block 35 in other embodiments, or may be implemented in analog domain after DAC 36 . can

RF front end 12 receives the output of power amplifier 17 and may include various components including one or more duplexers, switches (eg, formed of an antenna switch module), directional couplers, and the like. can Detailed examples of compatible RF front ends are shown with respect to FIGS. 4A and 4B and described below.

A directional coupler (not shown) in the RF front end 12 may be a dual directional coupler or other suitable coupler or other device capable of providing a sensed output signal to the mixer 38 . According to certain embodiments, including the illustrated embodiment, a directional coupler may provide both incident and reflected signals (eg, forward and reverse power) to mixer 38 . For example, a directional coupler may have at least four ports, an input port configured to receive signals generated by a power amplifier 17 , an output port coupled to an antenna 14 , and forward power a first measurement port configured to provide to the mixer 38 , and a second measurement port configured to provide reverse power to the mixer 38 .

The mixer 38 may multiply the sensed output signal by a reference signal (not illustrated in FIG. 3 ) of a controlled frequency to downshift the frequency spectrum of the sensed output signal. The downshifted signal may be provided to an ADC 39 , which may convert the downshifted signal into a feedback signal 47 in a digital format suitable for processing by the baseband processor 34 . As will be discussed in greater detail, by including a feedback path between the output of the power amplifier 17 and the input of the baseband processor 34 , the baseband processor 34 can be configured to optimize the operation of the power amplifier system 26 . may be configured to dynamically adjust the I and Q signals and/or a power control signal associated with the I and Q signals. For example, configuring the power amplifier system 26 in this manner may aid in controlling the power added efficiency (PAE) and/or linearity of the power amplifier 32 . Mixer 38, ADC 39, and/or other suitable components may perform a generally quadrature (I/Q) demodulation function in some embodiments.

Although power amplifier system 26 is illustrated as including a single power amplifier, the teachings herein are intended to be used in power amplifier systems including multiple power amplifiers, including, for example, multimode and/or multimode power amplifier systems. is applicable to

Additionally, although FIG. 3 illustrates a particular configuration of a transceiver, other configurations are possible, including, for example, configurations in which the transceiver 13 includes more or fewer components and/or a different arrangement of components. Do.

As shown, the baseband processor 34 may include a digital predistortion (DPD) table 40 , an equalizer table 41 , and a complex impedance detector 44 . The DPT table 40 may be stored in a non-volatile memory (eg, flash memory, read only memory (ROM), etc.) of the transceiver 34 accessible by the baseband processor 34 . . According to some embodiments, the baseband processor 34 accesses entries in the DPD table 40 to assist in linearizing the power amplifier 17 . For example, the baseband processor 34 selects appropriate entries in the DPD table 40 based on the sensed feedback signal 47 , and before outputting the transmit signal to the I/Q modulator 37 , the transmit signal adjust appropriately. For example, DPD may be used to compensate for certain non-linear effects of the power amplifier 17, including, for example, signal constellation distortion and/or signal spectrum spreading. According to certain embodiments, including the illustrated embodiment, the DPD table 40 implements a memoryless DPD, eg, the current output of the DPD corrected transmit signal depends only on the current input.

RF front end dictionary by characterizing with values obtained lookup Overview of Equalization Using Tables

Certain factors affect the duplexer of the RF front end 12 in combination with memory effects that are difficult to handle using a memoryless DPD entirely via the DPD table 40 , such as poor impedance matching exhibited by the power amplifier 17 . may contribute to the inherent group delay. To compensate for such memory effects and/or other factors contributing to nonlinearities or other signal degradation, power amplifier system 26 may utilize equalizer table 41 . Equalizer table 41 may be stored in non-volatile memory (eg, flash memory, read-only memory (ROM), etc.), which, depending on the embodiment, is the same as in which DPD table 40 is stored. memory, or a different memory. Although the DPD table 40 and the equalizer table 41 are shown residing within the baseband processor 34 for illustrative purposes, the memory devices comprising the tables reside at any suitable location on the transceiver 13 or , may reside elsewhere on the wireless device 11 .

The equalizer table 41 is populated during the characterization phase, which can be performed at the point of manufacture, for example the power amplifier system 26 is characterized under select input conditions. During characterization, power amplifier system 26 can be characterized at select complex impedance points, and specific parameters are recorded at each complex impedance point. For example, a programmable antenna tuner may be coupled to the power amplifier system 26 during characterization to set the desired complex impedance points. The system may be further characterized over other suitable parameters. As an example, in some embodiments, variables are additionally recorded across different channels and bands, which, among other gains, is an adaptation of the power amplifier system 26 to duplexer ripple across the transmit channel (eg, For example, adaptation of the DPT table 40) may be allowed to address some memory effects. A dual directional coupler or other suitable component may be used to capture the behavior of the power amplifier system 26 at each setpoint (eg, each characterized combination of phase, VSWR, channel, and band). Each of the recorded variables can be stored in a table along with the corresponding characterization setpoint values.

The recorded parameters forming the characterization information for each setpoint are: (1) the desired (eg, optimal) between the RF signal passed to the power amplifier 17 and the feed shaping signal passed through the supply control branch 48 ) relative delay; (2) the compression level of the power amplifier 17, which may correspond to the degree of compression that the power amplifier 17 is operating during peak envelope power; and (3) some or all of the maximum envelope power. 6A-6B provide examples of portions 600 , 650 of tables containing recorded parameters characterizing embodiments of a power amplifier system. Such tables may be used to form or generate part of the equalizer table 41 , for example. The characterization process will be described in more detail herein, for example with respect to FIGS. 4A , 4B , 5 , and 6A-6B .

During operation, complex impedance (eg, VSWR and/or phase) is detected with impedance detector 44 . Impedance detector 44 may be implemented in any suitable manner and may include digital or analog circuitry. For example, some or all of the impedance detector 44 may be implemented within the baseband processor 34 as shown. In other embodiments, some or all of the impedance detector resides in a feedback path external to the baseband processor 34 . Some examples of compatible components for detecting complex impedance are provided in US Pat. No. 8,723,531 entitled "Integrated VSWR Detector for Monolithic Microwave Integrated Circuits," which is incorporated herein by reference. One embodiment of a process for determining the complex impedance is shown and described with respect to FIG. 9 .

As shown, equalizer table 41 may include one or both of tx table 42 and supply control table 43 . The tx table 42 can be used to compensate the DPD table 40 to account for mismatches, non-linearities, etc., while the supply control table 43 can be used, for example, with the RF transmit signal 49 and the supply shaping signal. It can be used to control the delay of the delay component 33 of the supply control branch 48 based on the desired relative delay between them.

As represented by the dashed line extending from tx table 42 to tx signal 49 , tx table 42 directly computes tx signal 49 instead of or in addition to compensating DPT table 40 . It can be used to compensate. For example, in some cases, the power amplifier system 26 may be placed in a mode in which the DPD is turned off, and the tx table 42 is used to compensate for the tx signal 49 . As an example, DPD and envelope tracking are disabled until a certain transmit power level (eg, 100 milliwatts) is reached, at which point it is more energy inefficient to turn on envelope tracking and DPD. Moreover, in some cases, only one of the tx table 42 and the supply control table 43 is used at any given time. For example, the supply control table 43 is used in some embodiments only when the power amplifier system 26 is placed in the envelope tracking mode, while the power amplifier system 26 is not in the envelope tracking mode (eg For example, while in APT or fixed supply modes), only the tx table 42 is used. In some embodiments, equalizer table 41 includes only one of tx table 42 and supply control table 43 . Moreover, the information contained in the equalizer table 41 may be organized in a number of different ways. For example, although shown as separate tables, the tx table 42 and the supply control table 43 may be combined into a single table, or in other embodiments, the information provided in the equalizer table 41 is DPD It is combined with the table 40 .

For wideband signals such as 50 resource block (RB) LTE signals, memory effects can be a particularly significant problem due to loadline and delay variations across the RB frequency span. At VSWRs greater than 2:1, the memoryless DPD table 40 may be insufficient to handle AM-AM/AM-PM response variations across channels. In such cases, equalization of the baseband transmit signal (eg, I/Q signal) may be appropriate using, for example, equalizer table 41, which converts DPD table 41 into memory coefficients. can be increased The use of the equalizer table 41 implements an equalizer function that equalizes the compression level of the power amplifier 17 and/or achieves a desired (eg, optimal) delay of the power amplifier 17 across the band. can Thus, the equalizer table 41, which may include the above-described variables extracted across channels, provides equalizer functionality to large RB signals (eg 50 or 100 RBs or uplink CA 40 megahertz wide). can be used to perform According to certain embodiments, equalization can serve the dual role of adapting the DPD to work under various characterized conditions (eg, characterized VSWR conditions) as well as adding memory effect compensation to a memoryless DPD. there is. As will be explained, the equalizer function may have two paths, one for the RF transmit signal 49 , for example through the use of a TX table 42 , and one (eg, supply control) for the feed control path 48 , which may be, for example, an envelope tracker (via the use of a table 43 ).

According to some implementations, equalization table 41 includes separate gains and delays for each individual RB that apply only to RF transmit signal 49 , and there is no separate equalization for supply control path 48 . In another embodiment, equalization table 41 implements the function of accessing the truncated Volterra series via two separate paths: one for RF transmit signal 49 and one for envelope tracker path 48 ) is for Such an implementation may consist of a Finite Impulse Response (FIR) filter followed by a non-linear lookup table followed by another FIR. One block applies to the RF signal while the other block applies to the modulator signal. The FIR coefficients as well as the non-linear lookup tables are derived from the equalization table and the nominal condition memoryless DPD table.

Exemplary Front end modules

4A and 4B show exemplary front end modules 45 , any one of which is compatible with and may be incorporated into the systems shown in FIGS. 1-3 . 4A and 4B , the illustrated front end modules 45 include an input switch 55 , a set of power amplifiers 17 , a set of duplexers 50 , and an antenna switch module 51 . ), a dual directional coupler 52 , and a measuring switch 53 . The front end module 45 shown in FIG. 4B also includes an integrated antenna tuner 54 .

The input switch 55 switches the modulated RF transmit signal between the different power amplifiers 17 and corresponding duplexers 50 . The switched-in power amplifier 17 amplifies the received signal and transmits the amplified signal to the duplexer 50 . The duplexer 50 is configured to transmit the transmitted signal to the antenna switch module 51 . For simplicity, only the transmit path is shown in Figs. 4A-4B. However, it will be appreciated that the duplexer 50 is configured to allow bidirectional communication between the transceiver 13 and the antenna 14 . For example, the duplexer 50 may be additionally configured to accept a received signal from the antenna switch module 51 and transmit the received signal to the transceiver 13 for transmission. Duplexer 50 may additionally implement filtering or other suitable functionality. For example, duplexer 50 may provide rejection of transmitter noise at the receive frequency, isolation to prevent receive desensitization, and the like.

The antenna switch module 51 may be configured to electrically couple the antenna 14 to a selected transmit or receive path. Accordingly, the antenna switch module 51 may provide a number of switching functionalities associated with the operation of the front end module 45 . In certain embodiments, the antenna switch module 51 provides functionalities associated with, for example, switching between different bands, switching between different power modes, switching between transmit and receive modes, or some combination thereof. It may include a number of switches configured to provide The antenna switch module 51 may also be configured to provide additional functionality, including filtering and/or duplexing of signals.

The illustrated embodiment includes a dual directional coupler 52 that can provide a sensed output signal to the measurement switch 53 . The measuring switch 53 may be, for example, a single pole, double throw (SPDT) switch. According to certain embodiments, including the illustrated embodiment, a directional coupler may provide a measure of both incident and reflected signals (eg, forward and reverse power) in a transmit path. For example, the dual directional coupler 52 may have at least four ports, the four ports having an input port configured to receive signals generated by the power amplifier 17 , an output coupled to the antenna 14 . port, a first measurement port configured to provide forward power to the measurement switch 53 , and a second measurement port configured to provide reverse power to the measurement switch 53 . Although the illustrated embodiment includes a dual directional coupler 53 , other types of devices or combinations of devices may be used in other embodiments. In general, any device capable of detecting both incident and reflected signals (eg, forward and reverse power) in a transmit path may be used. The dual directional coupler 52 outputs a transmission signal for transmission to the antenna and outputs forward and reverse power signals to the measurement switch 53 . Measurement switch 53 switches between the two ports (eg, between detected forward and reverse power signals) and sends the switched output for delivery to the impedance detector.

In contrast to the front end module 45 shown in FIG. 4B , the front end module 45 shown in FIG. 4A does not include a programmable antenna tuner. In such an embodiment, memory effects such as those due to mismatch can be compensated for without the use of an integrated antenna tuner, using the appropriate use of the equalizer table 41 , thereby reducing cost and complexity, and also reducing the cost and complexity of the antenna tuner. Avoid losses that may be caused by consolidation. In such cases, a programmable antenna tuner may be temporarily coupled to the system, for example between the dual directional coupler 52 and the antenna to characterize the system. For example, an antenna tuner may be used during manufacturing to set complex impedance values for each characterization setpoint. The configuration shown in FIG. 4A may be used in combination with a pre-characterized equalizer table 41 in accordance with some embodiments to achieve a linearity improvement of at least 6 dB.

In some other embodiments, such as that shown in FIG. 4B , an integrated antenna tuner 54 is provided within the front end module 45 . Antenna tuner 54 includes circuitry comprising a pi-network and/or a T-network in some embodiments. Antenna tuner 54 may be programmable to provide impedance tuning and in some embodiments is used in combination with equalizer table 41 to compensate for memory effects. For example, programmable antenna tuner 54 may be used to provide coarse correction for certain nonlinearities (eg, AM-AM and/or AM-PM response variation, memory effects, etc.). Antenna tuner 54 may be tuned to provide an impedance tuning function such that power amplifier 17 provides VSWR compensation by recognizing a specific impedance closer to a desired value (eg, 50 ohms). Equalizer table 41, on the other hand, may be used to provide fine correction for certain non-linearities (eg, AM-AM and/or AM-PM response variation, memory effects, etc.). Including an integrated antenna tuner 54 may provide an added gain providing calibration of the dual directional coupler 52 . For example, the directionality of coupler 52 may be software or firmware augmented after calibration by de-embedding, linear transformation, or the like. The integrated tuner 54 may also provide improved performance under server mismatch conditions.

The characterization of the front end module 45 may be performed at any desired frequency, including each part in turn, or as one part per lot or one part per several lots to reduce calibration costs. can

front end pre-order the modules to characterize examples of methods

5 is a flow diagram 500 illustrating a process for precharacterizing a front end module. Process 500 may result in measurement of AM-AM and/or AM-PM response curves for each individual characterization state. One or more processors and/or other suitable components of a wireless device may implement certain portions of the process. For example, while certain portions of a process are described for illustration purposes as being implemented using specific components of the devices shown in FIGS. 3 and 4A-4B , the process is performed using the wireless device 11 of FIG. or using any other compatible wireless device 11 .

At block 502, the process includes using a programmable antenna tuner to set VSWR to an appropriate value for the current characterization setpoint state. For example, referring to the first row 602 shown in the exemplary partial equalizer lookup table 600 shown in FIG. 6A , using the antenna tuner, VSWR is set to a value corresponding to the current characterization setpoint state ( 1.2) can be set. If an integrated antenna tuner 54 is provided on the front end module 45 ( FIG. 4B ), the integrated tuner 54 may be used to adjust the VSWR. In case an integrated tuner is not provided ( FIG. 4A ), the antenna tuner may be temporarily attached to the front end module 45 for characterization purposes. The antenna tuner may be adjusted while monitoring the VSWR point using an integrated impedance detector 44 or other detector until a set point is reached.

At block 504, other parameters corresponding to the current characterization set point are set to appropriate values. For example, referring back to the exemplary setpoint corresponding to the first row 602 in the partial lookup table 600 shown in FIG. 6A , the phase, channel, and band of the complex impedance can be set to appropriate values (0 degrees, 20525, B5). Some or all of these set points may be achieved by adjusting the test input signal using a signal generator or other suitable tool.

At block 506, the system is characterized in the current characterization state. For example, a set of variables associated with the behavior of the front end module 45 is recorded at 506 . The variables may generally include any suitable variable or measure that may be used to compensate for non-linearities of the front end module 45 . For example, referring back to the first row 602 of the partial table 600 shown in FIG. 6A , the variables in such an exemplary embodiment are (1) the RF signal passed to the power amplifier 17 and supply control. the measured desired (eg, optimal) relative delay (1.11 nanoseconds [ns]) between the feed shaping signal passing through branch 48; (2) the compression level of the power amplifier 17 (2.0 dB), which can correspond to the degree of compression that the power amplifier 17 is operating during peak envelope power; and (3) maximum envelope power (29 decibel-milliwatts [dBm]). 6B , which includes another example of a partial lookup table 650 , the recorded variables are AM-AM coefficients (Var B) and AM-PM coefficients that also characterize AM-AM and AM-PM response curves. (Var C).

At block 508, the variables are written into the lookup table 41, or otherwise stored in non-volatile memory. In certain implementations, the variables are written directly to non-volatile memory in transceiver 13 upon characterization (eg, to form equalizer table 41 ). In other cases, the variables are written to some separate storage medium (eg, flash drive, disk drive, etc.) and downloaded to the baseband processor 34 or other suitable location within the wireless device 11 at a later point in time. . For example, in some cases, front end module 12 is characterized prior to assembly of wireless device 11 , and recorded values are downloaded to non-volatile memory accessible by baseband processor 34 or at a point of assembly of 11) or a part thereof is downloaded to some other suitable location within the wireless device 11 .

The process is then repeated for the next characterization setpoint. Referring back to FIG. 6A , the next setpoint may correspond to the second row 604 in the portion table 600 , with the phase value set at 45 degrees.

6A shows only one part of the characterization table that is swept with increasing values while keeping the out-of-phase setpoint parameters (VSWR, channel, and band) constant. To obtain a complete set of recorded values for use in the equalization table 41 by completing the characterization, the phase may be swept through additional values (eg, through 360 degrees) and other setpoint parameters It will be appreciated that each of them may also be swept while keeping some or all of the other parameters constant.

Although the partial tables 600 , 650 shown in FIGS. 6A-6B are referred to herein as forming part of the equalizer table 41 , the values in the partial tables 600 , 650 are equalized in some cases. It is not actually directly stored in the base table 41 . Instead, the recorded values from tables 600 , 650 are used to derive the values included in equalizer table 41 . For example, the AM-AM coefficients Var B and AM-PM coefficients Var C shown in the partial table 650 of FIG. 6B may be derived from other variables recorded during characterization.

According to certain embodiments, some or all of the characterization process 500 is performed while DPD is disabled.

7A and 7B show example processes for compensating for front end module operation using an equalizer table with values obtained during characterization of the front end module. For example, the processes may involve the use of equalizer table 41 shown in FIG. 3 , which may be obtained using the process shown in FIG. 5 , or a similar process. Although certain portions of the process are described for illustrative purposes as being implemented by the baseband processor 34 in the transceiver 13 of the power amplifier system 26 of FIG. 3 , the process may be implemented by any other suitable processor, such as FIG. 3 . by another processor in the transceiver 13 of the power amplifier system 26 of

Referring to FIG. 7A , at block 702 , the baseband processor 34 receives a complex impedance value (eg, VSWR and/or phase) sensed by the impedance detector 44 during signal transmission.

At block 704 , the baseband processor 34 uses the sensed impedance value to access the appropriate write from the equalizer table 41 . For example, referring to the partial tables 600 , 650 shown in FIGS. 6A-6B , the VSWR can be used to index the equalizer table 41 with other characterizing setpoint parameters (eg, phase, channel). , and band information). The phase, channel, and band information may be known by the baseband processor 34 based on current operating settings of the wireless device 11 , or in some cases one or more of the phase, channel, and band may be sensed It can be derived from a feedback signal.

At block 706, the baseband processor 34 applies a correction based on the accessed record. Depending on the embodiment, the records accessed from the equalization table 41 may include values for one or more of the variables recorded during characterization (e.g., RF vs. envelope tracker delay, compression level, and Pmax). . In such cases, the baseband processor 34 may process the variable to apply an appropriate correction. Taking power amplifier compression as an example, baseband processor 34 may condition the input signal to achieve a desired level of compression. For example, if a compression level of 2.0 dBm is specified for the accessed write, and the current gain is determined to be 2.7 dBm, then the baseband processor 34 can lower the input signal level appropriately. For the amount of delay offset, the baseband processor 34 may set the programmable delay of the delay component 33 according to the delay offset specified in the accessed write.

An indexed record may in some cases contain values derived from variables. For example, if the recording is used to compensate the DPD table, the correction values may be derived from the recorded variables and stored in the equalizer table 41 .

7B shows another process 750 for compensating for front end module operation using a pre-characterization lookup table. Similar to process 700 of FIG. 7A , baseband processor 34 receives the sensed complex impedance value at block 752 .

At block 754 , a coarse tuning function is performed using an antenna tuner 54 incorporated within the front end module 45 . As previously described with respect to FIG. 4B , the programmable antenna tuner 54 may use, for example, a power closer to a desired value (eg, closer to 50 ohms) to compensate to some extent the sensed mismatch. The impedance seen by amplifier 17 can be tuned to tune the load, thereby reducing VSWR.

At block 756 , the baseband processor 34 uses the sensed impedance value to access an appropriate write from the equalizer table 41 , similar to block 704 of process 700 of FIG. 7A . At block 758 , the baseband processor 34 applies fine tuning corrections based on the accessed write in a manner similar to block 706 of process 700 of FIG. 7B . For example, fine tuning may compensate for nonlinearities of a relatively smaller magnitude (eg, memory effects) that are addressed by coarse correction achieved using antenna tuner 54 .

power amplifier supply of mods examples

8A-8C show waveforms for power amplifiers operating in fixed supply voltage mode, average power tracking (APT) mode, and envelope tracking mode, respectively.

In FIG. 8A , a graph illustrates the voltage of the RF signal 804 and the power amplifier supply voltage 802 versus time. The RF signal 804 has a signal envelope 805 . It may be important for the power amplifier supply voltage 802 of the power amplifier to have a higher voltage level than that of the RF signal 804 . For example, providing a supply voltage to a power amplifier having a magnitude less than that of the RF signal 804 clips the signal, thereby creating signal distortion and/or other problems. Therefore, it is important that the power amplifier supply voltage 802 is greater than that of the signal envelope 805 . However, since the area between the power amplifier supply voltage 802 and the signal envelope 805 can represent lost energy that can reduce battery life and increase heat generated in the mobile device, the power amplifier supply voltage 802 can be It may be desirable to reduce the difference in voltage between the signal envelope 805 of the RF signal 804 and the RF signal 804 .

8B is a graph illustrating a power amplifier supply voltage 808 that is varied or varied with respect to a signal envelope 807 of an RF signal 810 . The graph shown in FIG. 8B may correspond to an average power tracking (APT) mode of power amplifier operation. In contrast to the power amplifier supply voltage 802 of FIG. 8A , the power amplifier supply voltage 808 of FIG. 4B is varied with discrete voltage increments during different time slots, illustrated by the dashed lines. The amplifier supply voltage 808 during a particular time slot may be adjusted, for example, based on the average power of the envelope 807 during that time slot. For example, a slot on the right may correspond to a lower power mode of operation than a slot on the left. By lowering the supply voltage during certain time slots, the APT operation may improve power efficiency compared to the fixed supply operation shown in FIG. 8A .

In FIG. 8C , the graph illustrates the voltage of the RF signal 816 and the power amplifier supply voltage 814 versus time. The graph shown in FIG. 8C may correspond to an envelope tracking mode of power amplifier operation. In contrast to the power amplifier supply voltage 802 of FIG. 8A , the power amplifier supply voltage 814 of FIG. 8B is varied or varied with respect to the signal envelope 815 . The area between the power amplifier supply voltage 814 and the signal envelope 815 of FIG. 8C is less than the area between the power amplifier supply voltage 802 and the signal envelope 805 of FIG. 8A, so the graph of FIG. 8C is larger It may be associated with a power amplifier system having energy efficiency. By tracking the supply voltage to the envelope, the envelope tracking operation can improve power efficiency compared to both the fixed supply operation shown in FIG. 8A and the APT mode shown in FIG. 8B .

8A-8C illustrate three examples of power amplifier supply voltage versus time, the teachings herein are applicable to other configurations of power supply generation. For example, the teachings herein are applicable to configurations where the supply voltage module limits the minimum voltage level of the power amplifier supply voltage.

complex Exemplary Methods for Determining Impedance

9 shows a flow diagram of an example method 900 for determining complex impedance. The determined impedance may be used, for example, to access the records in the equalizer table 41 and/or during the characterization process.

At block 902 , method 900 includes sampling an incident transmit signal path, eg, measurement switch 53 is switched to receive a forward power signal from a corresponding port of dual directional coupler 52 . . At block 904 , the method includes obtaining ideal I/Q data from the baseband processor 34 . For example, I/Q data may correspond to a data stream transmitted before the data stream is subject to mismatches and other effects within the front end module 45 . At block 906, the baseband processor 34 or other suitable component cross-correlates and time-aligns the ideal I/Q data and I/Q data received from the front end module 45 for the incident path. For example, the baseband processor 34 may use a subsample shift technique. At block 908 , the baseband processor 34 or other suitable component computes a complex phasor associated with the incident signal, which may be computed according to the example equation shown at block 908 of FIG. 9 .

At block 910 , the power amplifier system 26 switches the measurement switch 53 such that the switch couples into a reverse power signal from the corresponding port of the dual directional coupler 52 . At block 912 , the reflected transmit signal path is sampled. At block 914 , the method includes obtaining ideal I/Q data from the baseband processor 34 , wherein the ideal I/Q data causes the data stream to contain mismatches within the front end module 45 and other effects. It is possible to respond to the transmitted data stream before being affected by them. At block 916, the baseband processor 34 or other suitable component cross-correlates and time-aligns the ideal I/Q data and I/Q data received from the front end module 45 for the reflection path. For example, the baseband processor 34 may use a subsample shift technique. At block 918 , the baseband processor 34 or other suitable component computes a complex phasor associated with the reflected signal, which may be calculated according to the example equation shown at block 918 of FIG. 9 .

At block 920, the baseband processor 34, impedance detector 44, or other suitable component calculates a raw gamma (eg, complex impedance). The raw gamma can be calculated, for example, by dividing the calculated reflection complex phase by the incidence complex phase.

applications

Some of the embodiments described above provided examples in the context of mobile phones. However, the principles and advantages of the embodiments may be used for any other systems or apparatus having needs for power amplifier systems.

Such power amplifier systems may be implemented in a variety of electronic devices. Examples of electronic devices may include, but are not limited to, consumer electronic products, components of consumer electronic products, electronic test equipment, and the like. Examples of electronic devices may also include, but are not limited to, memory chips, memory modules, circuits of optical networks or other communication networks, and disk driver circuits. Consumer electronics include mobile phones, telephones, televisions, computer monitors, computers, handheld computers, personal digital assistants (PDA), microwaves, refrigerators, automobiles, stereo systems, cassette recorders or players, DVD players. , CD players, VCRs, MP3 players, radios, camcorders, cameras, digital cameras, portable memory chips, washers, dryers, washers/dryers, copiers, fax machines, scanners, multifunction peripherals, wrist watches, clocks, etc. , but not limited to these. In addition, electronic devices may include unfinished products.

conclusion

Throughout the detailed description and claims, unless the context clearly requires otherwise, the words "comprises", "comprising" and the like are used in an inclusive sense, as opposed to an exclusive or inclusive sense; That is, it should be construed as meaning "including, but not limited to". The word “coupled” as used herein generally refers to two or more elements that are either directly connected or can be connected as one or more intervening elements. Likewise, the word “connected,” as used herein generally, refers to two or more elements that are either directly connected or connected as one or more intervening elements. Additionally, the words "herein", "above", "below", and words of similar meaning, when used in this application, refer to the application as a whole and not to any specific portions of the application. will be. Where the context permits, words in the above detailed description using the singular or plural may also include the plural or singular respectively. The word “or” with respect to a list of two or more items encompasses all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of items in the list.

Moreover, as used herein, conditional language, such as "may", "could", "could", "may", "such as", "for example," " "such as" and the like generally refer to certain features, elements and/or states, including certain embodiments, and other embodiments, unless specifically indicated otherwise, or otherwise understood in context as used They are intended to suggest that they do not include. Thus, such a conditional language is such that features, elements, and/or states are required in any way for one or more embodiments, or that one or more embodiments have or have no author input or prompting. It is generally not intended to imply that such features, elements, and/or states necessarily include logic for determining whether they are included or performed in any particular embodiment.

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. Although specific embodiments of, and examples for, the invention have been described above for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the art will recognize. For example, although processes or blocks are presented in a given order, alternative embodiments may utilize systems having blocks or performing routines having steps in a different order, and some processes or blocks may be deleted, mobile, or deleted. may be added, subdivided, and/or modified. Each of these processes or blocks may be implemented in a number of different ways. Also, although processes or blocks are sometimes shown as being performed sequentially, such processes or blocks may instead be performed in parallel, or may be performed at different times.

The teachings of the present invention provided herein may be applied to systems other than those necessarily described above. Elements and acts of the various embodiments described above may be combined to provide further embodiments.

While specific embodiments of the present inventions have been described, these embodiments have been presented by way of example only and are not intended to limit the scope of the disclosure. Indeed, the novel methods and systems described herein may be embodied in various other forms; Moreover, 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 present disclosure. The appended claims and their equivalents are intended to cover such forms or modifications as come within the scope and spirit of the present disclosure.

Claims (20)

A power amplifier system comprising:
a modulator configured to generate a radio frequency transmission signal;
A front end module comprising: a power amplifier configured to amplify the radio frequency transmit signal to generate an amplified radio frequency transmit signal; and a coupler positioned between an antenna and the power amplifier, the coupler comprising the amplified radio frequency transmit signal configured to output a measure of both forward and reverse power associated with ;
one or more ratios storing an equalizer table having a plurality of entries generated during pre-characterization of the front end module under a plurality of characterization states corresponding to different input conditions volatile memory devices, wherein the one or more memory devices store a digital pre-distortion table configured to implement memoryless digital pre-distortion on the radio frequency transmission signal; and
(a) receive voltage standing wave ratio measurements derived from forward and reverse power output by the coupler; (b) based at least in part on the voltage standing wave ratio measurements in the equalizer table. and (c) entries accessed from the equalizer table to compensate for one or more memory effects present in the power amplifier system prior to amplification of the radio frequency transmission signal by the power amplifier; a processor configured to adjust the radio frequency transmission signal based on a predistortion table
A power amplifier system comprising a. 2. The power amplifier system of claim 1, wherein the equalizer table is generated using a programmable antenna tuner to tune the front end module to desired voltage standing wave ratio points. 2. The power amplifier system of claim 1, wherein the front end module does not include an integrated antenna tuner. 2. The power amplifier system of claim 1, wherein the front end module further comprises a programmable antenna tuner positioned between the antenna and the coupler. 2. The power amplifier system of claim 1, wherein the front end module further comprises one or more duplexers positioned between the power amplifier and the dual directional coupler and contributing to at least some of the memory effects. 5. The programmable antenna tuner of claim 4, wherein the programmable antenna tuner is adjustable to tune an impedance seen by the power amplifier to provide a coarse correction of nonlinearities within the power amplifier system; and adjusting the radio frequency transmission signal based on . 2. The power amplifier system of claim 1, wherein the coupler is a dual directional coupler. 2. The power amplifier system of claim 1, wherein the processor is further configured to adjust the radio frequency transmission signal by adapting values in the digital predistortion table based on accessed entries in the equalizer table. 5. The power amplifier of claim 1, further comprising an envelope tracking system configured to provide a power supply control signal to the power amplifier to control a voltage level of the power amplifier based on a shaped envelope signal; and the processor is further configured to adjust a delay between the radio frequency transmission signal and the supply control signal based on delay values included in the accessed equalizer table entries. A mobile device comprising:
a modulator configured to generate a radio frequency transmission signal;
a front end module comprising a power amplifier configured to amplify the radio frequency transmission signal to generate an amplified radio frequency signal and a coupler configured to receive the amplified radio frequency signal, the power amplifier providing power to the power amplifier configured to receive a power amplifier supply voltage to provide a power amplifier supply voltage, the coupler configured to output a measure of both forward and reverse power associated with the amplified radio frequency transmission signal;
an antenna configured to transmit the amplified radio frequency signal;
one or more non-volatile memory devices storing an equalizer table having a plurality of entries generated during precharacterization of the front end module under a plurality of characterization states corresponding to different input conditions, wherein the one or more memory devices are configured to storing a digital predistortion table configured to implement a memoryless digital predistortion on a frequency transmission signal; and
(a) receive voltage standing wave ratio measurements derived from the forward and reverse power output by the coupler; (b) access entries in the equalizer table based at least in part on the voltage standing wave ratio measurements; (c) prior to amplification of the radio frequency transmit signal by the power amplifier, the radio frequency transmit signal based on the accessed entries and the predistortion table to compensate for one or more memory effects present in a power amplifier system. a processor configured to tune
A mobile device comprising a. 11. The mobile device of claim 10, wherein the front end module further comprises one or more duplexers that contribute to at least some of the one or more memory effects. A power amplifier system comprising:
A front end module comprising: a power amplifier configured to amplify a radio frequency transmit signal to generate an amplified radio frequency transmit signal; a programmable antenna tuner coupled to the antenna; and a coupler positioned between the power amplifier and the antenna tuner. - the coupler is configured to output a measure of both forward and reverse power associated with the amplified radio frequency transmission signal, and the antenna tuner is configured to provide an approximate correction of non-linearities in the power amplifier system to the power amplifier. adjustable to tune the impedance seen by -;
one or more non-volatile memory devices storing an equalizer table having a plurality of entries generated during precharacterization of the front end module under a plurality of characterization states corresponding to different input conditions, wherein the one or more memory devices are configured to store a digital predistortion table configured to implement a digital predistortion on a frequency transmission signal; and
(a) receive voltage standing wave ratio measurements derived from the forward and reverse power output by the coupler, (b) access entries in the equalizer table based at least in part on the voltage standing wave ratio, ( c) a processor configured to, prior to amplification of the radio frequency transmit signal by the power amplifier, adjust the radio frequency transmit signal based on the accessed entries and the predistortion table
A power amplifier system comprising a. 13. The power amplifier system of claim 12, wherein the front end module further comprises a duplexer. 13. The power amplifier system of claim 12, wherein a duplexer is positioned between the power amplifier and the coupler. 13. The power amplifier system of claim 12, wherein the coupler is a dual directional coupler. 13. The power amplifier system of claim 12, wherein the processor is further configured to adjust the radio frequency transmission signal by applying values of the digital predistortion table based on accessed entries in the equalizer table. 13. The power amplifier system of claim 12, further comprising an envelope tracking system configured to provide a supply control signal to the power amplifier to control a voltage level of the power amplifier based on a shaped envelope signal and delay. 11. The mobile device of claim 10, wherein the equalizer table is generated using a programmable antenna tuner to tune the front end module to desired voltage standing wave ratio points. 11. The mobile device of claim 10, wherein the front end module does not include an integrated antenna tuner. 11. The mobile device of claim 10, wherein the front end module further comprises a programmable antenna tuner positioned between the antenna and the coupler.

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