Abstract: A distortion compensation apparatus including: a processor configured to generate a pre-distortion signal by compensating an input signal for a distortion based on a distortion compensation coefficient and a plurality of delayed signals obtained by delaying the input signal by a plurality of amounts of delay, and an amplifier configured to generate an amplified signal by amplifying the pre-distortion signal, wherein the processor calculates the distortion compensation coefficient based on the input signal, the pre-distortion signal, and the amplified signal, and calculates the plurality of amounts of delay based on the amplified signal.

Abstract: A system for time aligning widely frequency spaced signals includes a digital predistortion (DPD) processor and a power amplifier coupled to the DPD processor and operable to provide a transmit signal at a power amplifier output. The system also includes a feedback loop coupled to the power amplifier output. The feedback loop comprises an adaptive fractional delay filter, a delay estimator coupled to the adaptive fractional delay filter, and a DPD coefficient estimator coupled to the delay estimator.

Abstract: [Problem] To provide an amplifier and an amplification method in which degradation in the quality of the output signal is reduced.

Abstract: The scalable digital predistortion system and method provides compensation for the nonlinear distortions of power amplifiers and transmitters. The scalable digital predistortion system and its associated update algorithms provide scalability in terms of signal bandwidth and average power, allowing for low complexity updates following changes in the signal's bandwidth and/or power level. The method applies both memory polynomial functions and memoryless predistortion functions for compensating for the nonlinear distortions.

Abstract: Methods and apparatus are provided for amplifying an input signal. An electronic circuit system comprises a first circuit comprising a power amplifier, configured to receive a first branch of an input signal, and generate a first amplified signal based on the input signal of the first branch; a second circuit, configured to receive a second branch of the input signal, generate a cancellation signal based on the input signal of the second branch, and combine the first amplified signal and the cancellation signal to generate a second amplified signal. The second circuit comprises an interference re-construction module, which is configured to model an inverse characteristic of residual distortion and interference of the first circuit via a predefined re-construction function, and generate an anti-phased interference signal based on the input signal of the second branch and the predefined re-construction function. The cancellation signal is generated from the anti-phased interference signal.

Abstract: A digital predistorter for improving the performance of a narrow passband filter near the output is disclosed. The digital predistorter provides amplitude correction to the signal based on the characteristics of the passband filter. A filter group delay predistorter may also be employed to correct group delay variation introduced by the narrow passband filter.

Abstract: The present invention relates to a digital pre-distortion apparatus, including: a coefficient control unit for setting coefficients in a look-up table, the coefficients minimizing a difference of an input signal to a power amplifier and an exponentiation of the sum of a first absolute output signal having the first number of delays and a second absolute output signal having the second number of delays, for an absolute signal of an output signal of a power amplifier; an adder for receiving a first absolute input signal having the first number of delays and a second absolute input signal having the second number of delays, for an absolute signal of the input signal of the power amplifier, and outputting the sum of the first absolute input signal and the second absolute input signal; and said look-up table, connected to the adder, for outputting result values according to the set coefficients in correspondence to the sum of the first absolute input signal and the second absolute input signal.

Abstract: Aspects of a method and system for power supply adjustment and polar modulation in a MIMO system are provided. In each RF transmit chain of a MIMO system that utilizes polar modulation, aspects of the invention may enable generating a signal representative of an amplitude of a pair of phase-quadrature baseband signals; and controlling a voltage and/or current regulator utilizing said generated signal. In this regard, a voltage and/or current supplied to a power amplifier and/or mixer of one or more of the transmit chains may be controlled based on the generated signal. Additionally, a gain of a power amplifier for each RF transmit chain may be controlled utilizing said signal representative of an amplitude. The signal representative of an amplitude may be generated by squaring each of the phase-quadrature baseband signals and calculating a square root of a sum of the squared signals.

Abstract: To generate amplitude modulation to phase modulation (AMPM) predistortion data that compensates for phase distortion in a power amplifier of a communication device, a test signal is amplified via the power amplifier. The amplified test signal is combined, by wave superposition, with a reference oscillator signal into a resultant signal. The resultant signal is an outcome of interference between the amplified test signal and the reference oscillator signal. The resultant signal power is measured using envelope information and, from the measurement, a predistortion phase shift is determined that when applied to the test signal maximizes the interference between the amplified test signal and the reference oscillator signal. AMPM predistortion data is generated to correspond with the predistortion phase shift.

Abstract: A circuit for providing a bias signal for a power amplifier includes a first input, a second input and an output. The first input is configured to receive an input signal to be amplified by the power amplifier. The second input is configured to receive the amplified input signal. The output is configured to provide the bias signal.

Abstract: A distortion compensation device includes: a distortion compensator configured to output, to a power amplifier, a predistortion signal obtained by performing distortion compensation processing on a transmission signal by using a distortion compensation coefficient, wherein the distortion compensator limits bands of a reference signal and a feedback signal so that the bands fall in a pass band and updates the distortion compensation coefficient based on an error between the reference signal and the feedback signal, the reference signal corresponding to the predistortion signal, the feedback signal corresponding to an output feedback of the power amplifier.

Abstract: A system and method of pre-distorting a signal applied to a power amplifier to compensate for distortion introduced by the power amplifier at different power settings, comprising pre-distorting the signal according to a pre-distortion polynomial, prior to amplification of the signal by the power amplifier; adaptively estimating and applying pre-distortion polynomial coefficients to the pre-distorter by saving successive iterations of adaptive estimation of the pre-distortion polynomial coefficients; and regularizing estimation of the pre-distortion polynomial coefficients over successive iterations according to a modified objective function that initially constrains growth in the magnitude of the pre-distortion polynomial coefficients and then relaxes the constraint in growth over successive iterations until estimation is reduced to a steady-state least squares estimation.

Abstract: The method of transmitting a TDD (time division duplex) configuration information on a plurality of component carriers (CC) by a base station in a wireless communication system supporting a plurality of the CCs according to the present invention includes determining at least one first CC index to be configured with an uplink-downlink configuration, which is identical with a uplink-downlink configuration of at least one CC configured to a different base station, among a plurality of the CCs configured to the base station; and configuring a CC corresponding to a frequency band of the determined at least one first CC index among a plurality of CCs configured to at least one user equipment with the uplink-downlink configuration, wherein the CC corresponding to the determined at least one first CC index is a CC configured to an identical frequency band between the base station and the different base station.

Abstract: A method for compensating the frequency dependent phase imbalance in a transmitter is provided. The transmitter processes a baseband signal. The method includes the following steps: (a) compensating the baseband signal with a predetermined delay amounts; (b) inputting the compensated baseband signal to an upconversion circuit to generate a radio frequency (RF) signal; (c) inputting the RF signal to a delay information extractor to obtain a correlation value related to the information of the predetermined delay amount; (d) changing the predetermined delay amount and compensating the baseband signal again with the changed predetermined delay amount, and performing steps (b) and (c) again to update the correlation value; and (e) selecting a candidate delay amount from the predetermined delay amount according to the correlation value, and compensating the transmitter by using the candidate delay amount.

Abstract: Since a high-frequency signal that is output from a high-frequency oscillator circuit section is detected in a detector circuit and a bias of a negative voltage is supplied from a bias circuit section to the high-frequency amplifier circuit section with a detection voltage that is detected, a negative power supply circuit such as a DC/DC converter or a peripheral circuit is not required, and since a negative bias voltage can be supplied to a high-frequency amplifier circuit, downsizing can be achieved with a low cost.

Abstract: Systems and methods for mitigating intermodulation distortion in a receiver include receiving, at processing electronics, a radio frequency signal. An envelope of the received signal is detected to form a rectified envelope signal. A portion of the envelope signal attributable to intermodulation distortion may be isolated from the envelope signal. The isolated distortion may be used to reduce the gain of the received radio frequency signal.

Abstract: The present invention relates to the field of communications technologies and discloses a data processing method and apparatus to obtain a DPD non-linear distortion compensation coefficient under a QPSK mode. The embodiments of the present invention receive a first data flow, and perform interpolation into the first data flow to obtain a second data flow; receive a third data flow, and calculate a data flow signal quality difference between the third data flow and the second data flow; and obtain a DPD non-linear distortion compensation coefficient according to the data flow signal quality difference and the third data flow or the second data flow. The embodiments of the present invention are applicable to the scenarios of obtaining a DPD non-linear distortion compensation coefficient in QPSK mode.

Abstract: A distortion compensation device includes a storage unit, an address generator, and a distortion compensation processor. The storage unit stores therein a distortion compensation coefficient for compensating distortion generated in an amplifier for amplifying an input signal. The address generator generates a first address based on a power value of the signal at a current time. Furthermore, the address generator delays, every time a new augend is input, the sum of the power value of the signal at the current time and the augend. The address generator generates a second address based on the sum obtained by calculating a new augend, from the delayed sum. The distortion compensation processor acquires a distortion compensation coefficient corresponding to a combination of the first address and the second address from the storage unit and performs distortion compensation processing on the signal by using the acquired distortion compensation coefficient.

Abstract: There is disclosed a method of generating a supply voltage (230) for a power amplifier (114) arranged to amplify an input signal (228), comprising: generating (104) a target supply voltage tracking the input signal (228); predistorting (400) the target supply voltage to compensate for effects on a supply voltage in the amplifier (114); and generating (102) the supply voltage for the amplifier (114) in dependence on the predistorted target supply voltage (414).

Abstract: The use of power-efficient transmitters to establish acoustic wave energy having low undesirable harmonics is achieved by adjusting the transmitter output waveform to minimize the undesirable harmonics. In one embodiment, both the timing and slope of the waveform edges are adjusted to produce the desired output waveform having little or no second harmonics. In the embodiment, output waveform timing adjustments on the order of fractions of the system clock interval are provided. This then allows for very fine control of a coarsely produced waveform. In one embodiment, the user can select the fine tuning to match the transmitter output signal to a particular load transducer.

Abstract: Self-jamming interference associated with a transmitted signal of an aggressor transmitter may affect a received signal of a victim receiver in a communication device. A victim receiver may obtain a non-linear interference cancelation (NLIC) signal from an aggressor transmitter of a communication device. The NLIC signal may be based, at least in part, on a source transmit signal that has been distorted by digital pre-distortion (DPD) at the transmitter. An NLIC unit may reconstruct a cancelation signal based on the NLIC signal. A receiver may remove the cancelation signal from a received signal.

Abstract: A distortion compensation circuit compensates for the distortions generated by the dispersion-slope of an optical component and the frequency chirp of an optical transmitter. The dispersion compensation circuitry can be utilized in the optical transmitter, the optical receiver and/or at some intermediate point in a fiber-optic network. One embodiment of the compensation circuit utilizes a primary electrical signal path that receives at least a portion of the input signal and a delay line; and a secondary signal path in parallel to the primary path that receives at least a portion of the input signal and including: an amplifier with an electrical current gain that is proportional to the dispersion-slope of the optical component, an optional RF attenuator, an optional delay line, a “squarer” circuit, and a “differentiator” circuit.

Abstract: Disclosed herein is a low-cost digital predistortion apparatus using envelope detection feedback. The low-cost digital predistortion apparatus includes a digital predistortion unit and an envelope detection feedback unit. The digital predistortion unit converts the output of a predistorter into analog signals, frequency-modulates the analog signals into a pass band signal, and amplifies the frequency-modulated signal via a power amplifier. The envelope detection feedback unit converts the difference between the input and output of the power amplifier of the digital predistortion unit and the output of the power amplifier into baseband signals, respectively, converts the baseband signals into digital signals, estimates the nonlinear distortion characteristic output of the power amplifier, calculates a predistortion parameter that is used to compensate for the estimated nonlinear distortion characteristic output of the power amplifier.

Abstract: An automatic gain control circuit (5a) includes a peak detector circuit (10) that detects the peak voltage of the output signal from a variable gain amplifier (3), an average value detection and output amplitude setting circuit (11) that detects the average voltage of the output signals from the variable gain amplifier (3) and adds a voltage ½ the desired output amplitude of the variable gain amplifier (3) to the average voltage, and a high gain amplifier (12) that amplifies the difference between the output voltage of the peak detector circuit (10) and the output voltage of the average value detection and output amplitude setting circuit (11) and controls the gain of the variable gain amplifier (3) using the amplification result as a gain control signal. The peak detector circuit (10) includes transistors (Q1, Q2, Q3), a current source (I1), and a filter circuit. The filter circuit includes a series connection of a resistor (Ra) and a capacitor (C1).

Abstract: An amplifier module is expressed by a model having a first filter that is a linear time-invariant filter for limiting the bandwidth of an input signal, an amplifier unit that amplifies a signal output from the first filter, and a second filter that is a linear time-invariant filter for limiting the bandwidth of a signal output from the amplifier unit. A memoryless amplifier unit calculates an output from the amplifier module when being memoryless, using AM-to-AM distortion and AM-to-PM distortion of the amplifier unit. A cross-correlation calculating unit calculates a correlation between the signal output from the amplifier module and the output calculated by the memoryless amplifier unit and calculates an estimate of a transfer function of the first filter and the second filter. A distortion compensating unit compensates the input signal based on the estimate of the transfer function and outputs the signal to the amplifier module.

Abstract: An emphasis signal generating circuit includes: a branch circuit configured to split a signal into a plurality of paths; a delay circuit provided in one or more of the paths into which the signal has been split by the branch circuit, the delay circuit being configured to delay one or more signals; a phase compensation circuit provided in one or more of the paths into which the signal has been split by the branch circuit, the phase compensation circuit having such characteristics that a transmission intensity of a signal is low in a low frequency band and is high in a high frequency band; and an addition/subtraction circuit configured to perform addition and/or subtraction of signals from the plurality of paths and output a result.

Abstract: Example embodiment of the systems and methods of linear impairment modeling to improve digital pre-distortion adaptation performance includes a DPD module that is modified during each sample by a DPD adaptation engine. A linear impairment modeling module separates the linear and non-linear errors introduced in the power amplifier. The linear impairment model is adjusted during each sample using inputs from the input signal and from a FB post processing module. The linear impairment modeling module removes the linear errors such that the DPD adaptation engine only adapts the DPD module based on the non-linear errors. This increases system stability and allows for the correction of IQ imbalance inside the linear impairment modeling, simplifying the feedback post-processing.

Abstract: A method and apparatus for characterized pre-distortion calibration is provided. The method begins with the selection of a number of devices to be characterized. The number of devices selected may be a subset of a larger group of devices. The selected number of devices is then characterized. The method avoids characterizing the large group of devices. The calibration of the group of devices is then based on the characterization of the selected number of devices.

Abstract: A circuit in a transmitter with multiple power amplifiers includes multiple individual linearizer circuits each receiving a corresponding input signal and each providing a conditioned input signal to a corresponding power amplifier. The linearizer circuit each include: (a) a pre-distortion circuit receiving (i) the corresponding input signal and (ii) the output signal of a corresponding power amplifier, and providing a pre-distortion signal; (b) a cancelation circuit receiving an interfering signal and providing a cancelation signal; and (c) a combination circuit that combines the cancelation signal and the pre-distortion signal to provide a conditioned input signal to the corresponding power amplifier.

Abstract: There is disclosed a method of determining an AM-PM distortion measurement for an amplifier, the method comprising: generating a test waveform to be provided to the input of the amplifier; periodically puncturing the test waveform with a fixed-level reference signal to generate a modified test waveform which alternates between test periods in which a portion of the test waveform is present and reference periods in which the fixed-level reference signal is present; measuring the amplifier AM-PM distortion in a test period; measuring the phase difference between the input and the output of the amplifier in reference periods either side of the test period; estimating a phase error in the test period in dependence on phase differences measured in the reference periods; and estimating the true amplifier AM-PM distortion by removing the estimated phase error from the measured amplifier AM-PM distortion.

Abstract: Correction of quadrature errors associated with digital communications systems. A correction network may correct a difference between a transmission characteristic of an in-phase signal path and a transmission characteristic of a quadrature signal path. The quadrature signal path may be for the transmission of in-phase and quadrature parts of a signal and the signal comprising frequency components within a baseband. The correction network may include an in-phase input port, a quadrature input port, an in-phase output port and a quadrature output port. Each input port may be connected to each output port by a digital filter network, which may include a set of filter tap coefficients and configuration means for configuring values of the coefficients. Frequency dependent quadrature impairments, e.g., due to the analogue components of a quadrature up-converter or down-converter, may be corrected by suitable control of the coefficients.

Abstract: A distortion compensation apparatus for performing distortion compensation processing by applying the inverse properties of distortion properties of the power amplifier to a transmission signal to be input to a power amplifier, includes a plurality of distortion compensation coefficient storage units configured to store a plurality of distortion compensation coefficients used for the distortion compensation processing, an offset correction processing unit configured to subject the distortion compensation coefficient stored in each of the plurality of distortion compensation coefficient storage units to offset correction processing, and to generate distortion compensation coefficients in the case that the offset correction processing has not been performed, corresponding to plurality of distortion compensation coefficient storage units, in a pseudo manner and a distortion compensation processing unit configured to subject the transmission signal to the distortion compensation processing based on the distortion

Abstract: A predistortion circuit is for providing distortion correction in a presence of harmonics. The predistortion circuit includes an input for receiving a digital input signal; an output for providing a digital output signal to an up-conversion element that produces harmonic terms operably coupled to a non-linear device; and a processor operably coupled to an output of the non-linear device for receiving an output radio frequency signal therefrom and arranged to determine a digital correction to be applied to the digital input signal. The processor is further arranged to determine the digital correction that includes a plurality of in-phase and quadrature cross-terms of the digital input signal where terms of a same order have different co-efficients.

Abstract: A distortion compensating apparatus including: a processor to generate a compensated signal by performing distortion compensation on an input signal, based on a distortion compensation coefficient depending on the input signal, to separates the compensated signal into a first signal and a second signal that have constant amplitude and that have a phase difference based on amplitude of the compensated signal, to generate a third signal by multiplying the first signal by a first coefficient, and to generate a fourth signal by multiplying the second signal by a second coefficient, and a combiner to generate a seventh signal by combining the fifth signal and the sixth signal which are generated by amplifying the third signal and the fourth signal, wherein the processor is further configured to calculate the distortion compensation coefficient, the first coefficient, and the second coefficient, based on the third signal, the fourth signal and the seventh signal.

Abstract: Described herein are methods and system for providing digital non-linear loop control. In one embodiment, system with digital non-linear loop control comprises a parameter control circuit configured to modify a signal based on a control signal, a processing circuit configured to process the signal, and a parameter measurement circuit configured to measure a parameter value of the signal. The system also comprises a digital non-linear control circuit configured to compare the measured parameter value with a desired parameter value, to determine a control signal value based on the comparison using a lookup table (LUT) that characterizes a non-linear control response of the system, and to output the control signal to the parameter control circuit based on the determined control signal value.

Abstract: An integrated circuit (IC) includes first and second circuits. The first circuit is manufactured using a process, has an input and an output, and has a first nonlinearity. The second circuit is manufactured using the process, has a first terminal connected to the output of the first circuit and a second terminal connected to the input of the first circuit, and has a second nonlinearity. The second nonlinearity (i) is equal and opposite to the first nonlinearity and (ii) cancels the first nonlinearity.

Abstract: An apparatus and a method select and use parameter values for an RF power amplifier linearizer to pre-distort the input signals of a power amplifier, so as to achieve a linear output response in the power amplifier. The apparatus and the method select from a number of sets of parameter values, each set of parameter values corresponding to a different output power range of the power amplifier. The set of parameters include a coefficient vector tailored for the particular output power range for that set. The power amplifier input power is repeatedly measured and filtered at various time intervals. The input power measurements may be filtered by a fast attack/slow decay filter, which follows the peaks of the measurements under operation of the fast attack portion of the filter and provides a low variance during operation of the slow decay portion of the filter.

Abstract: To effectively control the amplitude vs. power supply voltage characteristics, for example, in an ET amplifier.

Abstract: Various embodiments provide for systems and methods for increased linear output power of a transmitter. An exemplary wireless communications system for transmitting an input signal comprises a predistorter module, a GaN power amplifier, a coupler, and an antenna. The predistorter module is configured to detect existing distortion by comparing the input signal to a feedback signal and generate a correction signal. The predistorter may adaptively adjust its operation to minimize the existing distortion due to GaN power amplifier nonlinear characteristics. The result is that the GaN power amplifier may send a power signal of improved linearity to the antenna. The coupler is configured to sample the amplified signal from the GaN power amplifier to generate the feedback signal. The antenna is configured to transmit the amplified signal.

Abstract: In one implementation, a power amplifier may include a gain device to receive an input signal and to output an amplified signal, and a compensation device coupled to the gain device to compensate for a change in a capacitance of the gain device occurring due to a change in the input signal. The power amplifier may be formed using a complementary metal oxide semiconductor (CMOS) process.

Abstract: A power encoder includes an amplitude-phase splitter for splitting an input signal into an envelope signal and a phase modulated signal, and a pre-distortion unit for distorting the envelope signal using a look-up table (LUT) to produce a distorted envelope signal. The power encoder also includes a digital converter for combining the distorted envelope signal with the phase modulated signal to produce a distorted input signal, a pulse width modulator (PWM) for modulating the distorted input signal according to the transformation function to produce a modulated signal, and a switch mode power amplifier for amplifying the modulated signal. The look-up table stores a non-linear mapping of a transformation function and a relationship between the distorted input signal and the modulated signal is non-linear.

Abstract: A transformer has first and second transformer windings including multiple differential ports. Each of the first and second transformer windings include a first transformer half-winding coupled to a first differential port of the differential ports. Each of the first and second transformer windings also include a second transformer half-winding coupled to a second differential port of the differential ports. Each of the first and second transformer windings is divided symmetrically at a common node to form the respective first and second transformer half-windings. The first transformer half-winding is configured to form one half of an inductance in each of the first and second transformer windings. The second transformer half-winding is configured to form another half of the inductance in each of the first and second transformer windings. The common node of the first transformer winding is configured to receive a supply voltage.

Abstract: A system linearization assembly generally includes a filter that is coupled to a measuring device. The filter is configured to receive a signal that includes a time varying parameter representing a plurality of frequency components including at least one component caused by non-linear intermodulation distortion, such as an odd-order intermodulation distortion component. The filter is also configured to isolate at least one harmonic of the frequency components with the same order as the component caused by non-linear intermodulation distortion. The measuring device is configured to measure at least one parameter of the isolated harmonic. The system linearization assembly also includes a controller coupled to the measuring device. The controller is configured to modify, for example by minimizing, the signal from the determined measurement to facilitate a modification, such as a reduction, of the component caused by non-linear intermodulation distortion.

Abstract: Circuitry for reducing power consumption is described. The circuitry includes a power amplifier. The circuitry also includes a predistorter coupled to the power amplifier. The circuitry further includes a power supply coupled to the power amplifier. The circuitry additionally includes a controller coupled to the power amplifier, to the predistorter and to the power supply. The controller captures a transmit signal and a feedback signal concurrently and determines a minimum bias voltage from a set of voltages and a predistortion that enable the power amplifier to produce an amplified transmit signal in accordance with a requirement.

Abstract: A radio frequency channel amplification module for communication satellite, comprises an input configured to convey an input radio frequency signal, an output configured to restore a pre-amplified output radio frequency signal intended to power a travelling wave tube amplifier that can be equipped with linearization means with predistortion, at least one first upstream gain control module arranged downstream of the input and one second downstream gain control module arranged downstream of the first upstream gain control module and upstream of any linearization means by predistortion. The channel amplification module also comprises an instantaneous power limiter intended to clip the peaks of the input radio frequency signals with a level exceeding a determined threshold value, the instantaneous power limiter being arranged in series between said first upstream gain control module and said second downstream gain control module.

Abstract: Circuits and techniques to linearize the operation of an RF power amplifier are described. A linearizer circuit may include a non-amplification signal path which includes a delay line and an amplification signal path which includes at least one amplifier stage. In some embodiments, the amplification signal path may include an odd number of amplification stages. The linearizer may be used to precondition an input signal of an RF power amplifier in a manner that improves the overall linearity of operation.

Abstract: An apparatus comprises an amplifier and a pre-distortion circuit coupled to an input of the amplifier. A saturation value of an input signal corresponds to a maximum output power of an output signal of the amplifier. An input target value of the input signal is determined according to the saturation value. The input target value is determined by subtracting an offset from the saturation value or by multiplying a ratio by the saturation value. An average value or an RMS value of the input signal is controlled to be substantially equal to the input target value. A method comprises determining an input target value according to a saturation value, and controlling an input signal according to the input target value.

Abstract: In an embodiment, a circuit includes a variable group delay configured to delay a wideband input signal to obtain a delayed input signal; a wideband operational amplifier configured to determine an error signal based on a difference between the delayed input signal and a linearized power amplifier output; a feedback amplifier configured to amplify the error signal to obtain an amplified error signal; and a directional combiner configured to combine the amplified error signal with the power amplifier output to obtain the linearized power amplifier output.

Abstract: A distortion compensation apparatus includes a pre-distorter, a gain control unit, and a learning unit. The pre-distorter adds distortion according to compensation coefficients to individual input signals prior to the input signals being input to a power amplifier. The gain control unit applies gain control to individual feedback signals fed back from the power amplifier according to a maximum level of the feedback signals within a time frame. The learning unit updates the compensation coefficients used by the pre-distorter, using the feedback signals subjected to the gain control by the gain control unit.

Abstract: An amplifier includes two input terminals to receive a differential, two-tone transmission signal; two output terminals; a coil having terminals connected with the input terminals respectively, and a center tap; a first transistor having the gate connected with one terminal of the coil, and the output terminal connected with one output terminal; a second transistor having the gate connected with the other terminal of the coil, end the output terminal connected with the other output terminal; a diode having a terminal connected with the center tap; and a bias circuit connected with the other terminal of the diode to output a gate voltage to turn on the first and second transistors. The diode adjusts the terminal voltage depending on a signal level of a double harmonic wave of the transmission signal supplied to the terminal of the diode from the center tap.