Abstract: A radio-frequency circuit includes a first power amplifier that outputs a first transmission signal and a second power amplifier that outputs a second transmission signal having a frequency different from a frequency of the first transmission signal. In a period in which the first transmission signal the second transmission signal are simultaneously outputted, at least one of the first power amplifier or the second power amplifier reduces transmission power of the at least one of the first power amplifier or the second power amplifier to cause a power component of intermodulation distortion superimposed on a transmission signal output from the first power amplifier and the second power amplifier to be less than or equal to a threshold value.

Abstract: The present disclosure provides a method for compensating gain flatness of a transceiver including: a method for compensating gain flatness of a receiver, which compensates gain flatness of a receiving channel by using a complex-coefficient FIR filter in digital domain; and a method for compensating gain flatness of a transmitter, which compensates gain flatness of a transmitting channel by using a complex-coefficient FIR filter in digital domain. The method according to the present disclosure can balance compensation accuracy and calculation amount flexibly, and can focus on compensating the gain flatness at an edge of a frequency band, obtaining good performance with less calculation amount.

Abstract: A telecommunications system may include a distortion cancellation subsystem for use with a circulator device coupling an antenna to a transmit path and a receive path. The distortion cancellation subsystem may include a correction circuit and a cancellation circuit. In some aspects, the correction circuit may include a processing device or adaptive filter to correct imperfections in transmit signal samples generated by directional couplers. The correction circuit may also include a summing device to remove receive signal components from the transmit signal samples. The cancellation circuit may receive the output signal of the correction circuit via an adaptive filter. The output of the adaptive filter may be summed with a receive signal to minimize distortion of the receive signal.

Abstract: An active cancellation system may be utilized to cancel interference, such as from transmitter leakage or self-interference in a transceiver of an electron paramagnetic resonance (EPR) spectrometer. The active cancellation system may be inserted between the transmitter and receiver. The active cancellation system may receive the output of the transmitter, and generate a cancellation signal with the same amplitude, but phase shifted relative to the self-interference signal. The cancellation system may include an attenuator/amplitude tuner, buffer, VQ generator, and phase shifter.

Abstract: An amplification device includes a plurality of amplifiers arranged in parallel, a plurality of directional couplers coupled to the plurality of amplifiers, respectively, and configured to receive output signals of the plurality of amplifiers, respectively, a phase shifter coupled to a first directional coupler of the plurality of directional couplers, and configured to generate a first signal to which a phase of an output signal of the first directional coupler is inverted, a combining circuit coupled to the phase shifter and a second directional coupler of the plurality of directional couplers, and configured to combine an output signal of the phase shifter and an output signal of the second directional coupler, and a processor configured to control at least one of the plurality of amplifiers so that a level of an output signal of the combining circuit is minimized.

Abstract: A system and method for receiving a signal, comprising an input adapted to receive a radio frequency signal having a strong interferer; a signal generator, adapted to produce a representation of the interferer as an analog signal generated based on an oversampled digital representation thereof; and a component adapted to cancel the strong interferer from radio frequency signal based on the generated analog signal to produce a modified radio frequency signal substantially absent the interferer. The system typically has a nonlinear component that either saturates or produces distortion from the strong interferer, which is thereby reduced. The system preferably employs high speed circuits which digitize and process radio frequency signals without analog mixers.

Abstract: A bidirectional amplifier includes first and second ports, with a first summing node connected to the first port and a second summing node connected to the second port. First and second gain stages are connected between the first and second summing nodes, respectively, and a first node. First and second feedback stages are also connected between the first and second summing nodes, respectively, and the first node. The amplifier operates in a first mode in which an amplified version of a signal applied to the first port is provided at the second port, or a second mode in which an amplified version of a signal applied to the second port is provided at the first port. The first and second gain stages are preferably first and second common emitter cascode arrangements, and the first and second feedback stages are preferably first and second emitter followers.

Abstract: A device can include a first component to receive, from a first network device, a first upstream optical signal. The first upstream optical signal can be associated with a designated time slot of the first network device. The device can include a second component to receive, from the first component, the first upstream optical signal. The second component can split the first upstream optical signal into a second upstream optical signal and a third upstream optical signal. The second component can provide, to a second network device, the third upstream optical signal. The third upstream optical signal is not associated with the designated time slot of the first network device.

Abstract: A controller for controlling a signal processor includes a transformation unit and a control unit. The transformation unit is configured to generate at least one amplitude-modulation-to-phase-modulation-distortion within a signal, output by using the signal processor according to a signal processing, based on generated at least one amplitude-modulation-to-amplitude-modulation-distortion of the signal. The control unit is configured to adjust the signal processing of the signal processor so as to minimize the at least one amplitude-modulation-to-phase-modulation-distortion.

Abstract: A communication device, such as a smartphone or tablet, includes a communication interface with noise cancellation logic. The noise cancellation logic includes a lead path and a reference path. A signal source provides a signal to the lead path and the references path. The signal is amplified along the lead path and the reference path. Distortion is imparted onto the signal during amplification on the lead path. A correction signal based on the difference between the amplified signal on the lead path and the amplified signal on the reference path is generated by the noise cancellation logic. The correction signal may reflect to distortion imparted during amplification on the lead path. The correction signal is differentially combined with the amplified signal on the lead path to attempt to remove the distortion and generate an output.

Abstract: A radio frequency amplification stage comprising: an amplifier for receiving an input signal to be amplified and a power supply voltage; and a power supply voltage stage for supplying said power supply voltage, comprising: means for providing a reference signal representing the envelope of the input signal; means for selecting one of a plurality of supply voltage levels in dependence on the reference signal; and means for generating an adjusted selected power supply voltage, comprising an ac amplifier for amplifying a difference between the reference signal and one of the selected supply voltage level or the adjusted selected supply voltage level, and a summer for summing the amplified difference with the selected supply voltage to thereby generate the adjusted supply voltage.

Abstract: Systems and methods for suppressing transmitter noise in a receive band of a co-located receiver that are suitable for wideband applications are disclosed. In one embodiment, a transmitter is configured to upconvert and amplify a digital transmit signal to provide an analog radio frequency transmit signal at an output of the transmitter that includes a desired signal in a transmit band of the transmitter and transmitter noise in a receive band of a main receiver. The main receiver is configured to amplify, downconvert, and digitize an analog radio frequency receive signal to provide a digital receive signal. The digital feedforward transmit noise cancellation subsystem is configured to process the digital transmit signal to generate a digital transmitter noise cancellation signal that is representative of the transmitter noise in the receive band and is subtracted from the digital receive signal to thereby provide a compensated digital receive signal.

Abstract: Systems and methods for suppressing transmitter noise in a receive band of a co-located receiver that are suitable for wideband applications are disclosed. In one embodiment, an analog radio frequency transmit signal output by a transmitter includes a desired signal in a transmit band of the transmitter and transmitter noise in a receive band of a main receiver. A secondary receiver obtains a secondary receiver input signal that is representative of at least the transmitter noise in the receive band of the main receiver and outputs a digital feedforward signal. A digital feedforward transmit noise cancellation subsystem generates a digital transmitter noise cancellation signal that is representative of the transmitter noise in the receive band based on the digital feedforward signal and subtracts the digital transmitter noise cancellation signal from a digital receive signal output by the main receiver to thereby provide a compensated digital receive signal.

Abstract: A technique for a reconditioning equalizer filter for non-constant envelope signals is described. The input to a transmitter chain is modified by a reconditioning equalizer filter, prior to being applied to the transmitter. The reconditioning equalizer filter modifies and smoothens the amplitude of the signal. The modified and smoothened signal has its peaks reduced which results in lower Crest Factor. The input to the reconditioning equalizer filter could be a baseband, intermediate frequency (IF) or radio frequency (RF) signal. When the signal is an IF or RF signal, it needs to be down-converted to baseband before being applied to the reconditioning equalizer filter. The reconditioning equalizer filter could be performed in a digital or analog domain.

Abstract: A radio frequency (RF) transmitter is provided. The RF transmitter includes first and second drivers that are configured to receive first and second sets of complementary RF signals. Restoration circuits are coupled to the first and second drivers, and a bridge circuit is coupled to the first and second restoration circuits. By having the restoration circuits and the bridge circuit, a common mode impedance and a differential impedance can be provided, where the common mode impedance is lower than the differential impedance.

Abstract: Disclosed herein are systems and methods for recovering a sub-carrier signal from a multiplexed signal having an embedded pilot tone signal. The recovery system includes circuitry for recovering a pilot signal from the received multiplexed signal, for generating a frequency-doubled signal from the recovered pilot signal, and for phase-shifting the frequency-doubled signal by a pre-determined phase difference from the embedded pilot tone signal. Another recovery system includes circuitry for recovering a pilot signal from the received multiplexed signal, for phase-shifting the pilot signal by a pre-determined phase difference from the embedded pilot tone signal, and for generating a frequency-doubled signal from the phase-shifted signal.

Abstract: A channelized amplification system and method for mitigating non-linear amplification effects and controlling spectral re-growth is disclosed. A channelized amplifier system includes a frequency divider, a plurality of distributors coupled to the frequency divider, and a plurality of amplification modules coupled to the plurality of distributors. Each of the plurality of amplification modules includes a plurality of channelized non-linear amplifiers, a frequency combiner having a plurality of band-pass filters and coupled to the plurality of channelized non-linear amplifiers, and a band-pass filter coupled to the frequency combiner.

Abstract: An apparatus comprising a first circuit configured to receive a signal and output a first output signal, a second circuit configured to receive the same signal and output a second output signal with a phase delay compared to the first signal, and a combiner configured to combine said first and second output signals to provide a combined signal, wherein said phase delay is controlled such that an amplitude of said combined signal is controlled.

Abstract: Disclosed herein are systems and methods for recovering a sub-carrier signal from a multiplexed signal having an embedded pilot tone signal. The recovery system includes circuitry for recovering a pilot signal from the received multiplexed signal, for generating a frequency-doubled signal from the recovered pilot signal, and for phase-shifting the frequency-doubled signal by a pre-determined phase difference from the embedded pilot tone signal. Another recovery system includes circuitry for recovering a pilot signal from the received multiplexed signal, for phase-shifting the pilot signal by a pre-determined phase difference from the embedded pilot tone signal, and for generating a frequency-doubled signal from the phase-shifted signal.

Abstract: A power amplifier controller circuit controls a power amplifier based upon an amplitude correction signal indicating the amplitude difference between the amplitude of the input signal and an attenuated amplitude of the output signal. The power amplifier controller circuit comprises an amplitude control loop and a phase control loop. The amplitude control loop adjusts the supply voltage to the power amplifier based upon the amplitude correction signal. The RF power amplifier system may reduce the corrective action of the amplitude loop during periods of relatively rapid changes in amplitude, and thus distortion can be further reduced.

Abstract: A non-linear distortion signal contained in output signal components from a high-frequency power amplifier is detected, while a non-linear distortion signal is generated from a high-frequency signal to be amplified. Correlation between this non-linear distortion signal and the detected non-linear distortion signal is determined, and a control variable is calculated based on the signal thus obtained. The obtained control variable is multiplied by the generated non-linear distortion signal to generate a distortion compensation signal, which is added to the signal to be amplified. This provides a distortion compensation device capable of automatically maintaining optimum distortion compensation characteristics and rapidly achieving desirable distortion compensation.

Abstract: A pilot system and method is disclosed that increases the rate of convergence of the second loop alignment control in a feed forward amplifier. Both a pilot generation and detection system and search algorithm controlling the alignment are disclosed. By measuring the frequency of the generated pilot, phase information regarding the second loop cancellation transfer function can be inferred. Changes in the pilot frequency as the search algorithm makes steps in the second loop alignment indicate errors in the direction of the search. Using this pilot frequency measurement along with the existing log-power measurement of the residual pilot power improves the convergence speed because fewer steps will be made to reach the optimal alignment setting.

Abstract: A technique for a reconditioning equalizer filter for OFDM and non-OFDM signals is described. The input to a transmitter chain is modified by a reconditioning equalizer filter, prior to being applied to the transmitter. The reconditioning equalizer filter modifies and smoothen the amplitude of the signal. The modified and smoothen signal has its peaks reduced which results to lower Crest Factor. The input to the reconditioning equalizer filter could be a baseband, an intermediate frequency (IF) or radio frequency (RF) signal. When the signal is an IF or RF signal it needs to be down converted to baseband before applied to reconditioning equalizer filter.

Abstract: An amplifying method and apparatus generates a plurality of constant envelope signals from an input signal and generates a plurality of pilot signals associated with the generated plurality of constant envelope signals, respectively. The plurality of pilot signals have predetermined amplitudes, predetermined phases, and predetermined frequencies, respectively, and the phases and frequencies are different from each other. The plurality of pilot signals are added to the generated plurality of constant envelope signals, and the sum is amplified. An amplitude or phase of one of the generated plurality of constant envelope signals is corrected using signal components included in the amplified plurality of constant envelope signals.

Abstract: Disclosed herein are systems and methods for recovering a sub-carrier signal from a multiplexed signal having an embedded pilot tone signal. The recovery system includes circuitry for recovering a pilot signal from the received multiplexed signal, for generating a frequency-doubled signal from the recovered pilot signal, and for phase-shifting the frequency-doubled signal by a pre-determined phase difference from the embedded pilot tone signal. Another recovery system includes circuitry for recovering a pilot signal from the received multiplexed signal, for phase-shifting the pilot signal by a pre-determined phase difference from the embedded pilot tone signal, and for generating a frequency-doubled signal from the phase-shifted signal.

Abstract: A predistorter includes: a divider that divides an input signal and supplies the divided input signal to a linear transmission path and a distortion generating path; a (2k?1)th-order distortion generator that raises the signal supplied to the distortion generating path to the (2k?1)th power to generate a distortion component; a vector adjuster that adjusts the amplitude and phase of the output of the (2k?1)th-order distortion generator; and an adder that sums up the output of the vector adjuster and the output of the linear transmission path to generate a predistorted signal r(t), in which the (2k?1)th-order distortion generator comprises: a (2k?1)th-order multiplier (27B4) that raises the divided signal to the (2k?1)th power; a lower-than-(2k?1)th-order multiplier (27B3, 27B2, 27B1) that raises the divided signal to the 5th, 3rd and 1st power, respectively; a vector adjuster (27C3, 27C2, 27C1) that adjusts the amplitude and phase of the output of the lower-than-(2k?1)th-order multiplier; and an adder (27D) t

Abstract: There is provided a feed-forward amplifier which enables a predistortion circuit to obtain sufficient distortion compensation effects even if ambient temperature or the like changes.

Abstract: A feed-forward amplifier having a signal cancellation loop including a cancellation node that includes a gain controller and a phase controller. Each controller provides a discrete tap steering signal and modulates the corresponding tap steering signal with a discrete tracer signal that takes on a preselected sequence of values. The sequence chosen so that the tracer signal is mutually orthogonal to each other tracer signal over a preselected period. A gain and phase adjuster connected to the outputs of the controllers provides a controlled gain change and phase shift in the signal cancellation loop, the magnitude of the gain change and phase shift controlled by the corresponding tap steering signals presented to the gain and phase adjuster by the controllers. A detector, the input of which is connected to the cancellation node and the output of which is connected to the controllers, outputs a measure of the envelope of the signal at the cancellation node.

Abstract: The present invention provides a digital (computational) branch calibrator which uses a feedback signal sensed from an RF transmit signal path following the combining stage of LINC circuitry of a transmitter to compensate for gain and phase imbalances occurring between branch fragment signals leading to the combiner. The calibrator feeds a quiet (zero) base band signal through the transmit path during the calibration sequence (i.e. a period when data is not transmitted) and adjusts the phase and gain of the phasor fragment signals input thereto by driving the sensed output power to zero. The calibration is performed by alternating phase and gain adjustments with predetermined (programmable) and multiple update parameters stages (speeds). A baseband modulation is preferably used to distinguish false leakage (e.g. due to local oscillator, LO, feed through and DC offset in the base band Tx) from imbalance leakage.

Abstract: A method and multiple carrier linear amplifier circuit reduces intermodulation distortion by sampling the multiple carrier linear amplifier radio frequency signal and detecting the sampled signal at frequency increments and quantizing and nulling the intermodulation distortion. The signal can have predetermined frequency increments fo . . . fi situated in at least one of predetermined sub-bands. The sampled radio frequency signal can be mixed with the local oscillator signal to target the centers of the multiple carriers and generate an intermediate frequency signal.

Abstract: An amplification apparatus that has a distortion detection loop that detects distortion components contained in an amplified signal to be amplified that is amplified by an amplifier 3, and a distortion removal loop that removes distortion components from the amplified signal, using the distortion components detected by the distortion detection loop, combines a reference signal (pilot signal) with the signal to be amplified, and performs control relating to distortion compensation, using said reference signal, to provide improved efficiency with respect to a configuration to perform control relating to distortion compensation, using a reference signal. A signal to be amplified is detected by amplification signal detection means 11˜13 and 21, and when it is detected by the amplification signal detection means that there is no input of a signal to be amplified, reference signal control means 21, 15 perform control to effect non-output of the reference signals.

Abstract: An L-C resonant circuit with an adjustable resonance frequency, having a capacitor and a first inductor electrically coupled together and a second inductor magnetically coupled to the first inductor. Additionally, there is a control circuit to sense a signal representing a first current flowing through the first inductor and to force through the second inductor a second current that is a replica of the first current for setting the adjustable resonance frequency of the L-C resonant circuit.

Abstract: Systems and methods are provided for controlling gain compensation over temperature and frequency variations. A variable amplifier may be used to receive a control signal and an input signal. The variable amplifier may be operable to apply a gain to the input signal to generate an output signal, wherein the gain is a function of the control signal. A summation module may be used to combine a gain reference signal and a gain variation signal to generate the control signal. The gain reference signal may be calibrated at a reference temperature and a reference frequency. A gain calibration module may be used to output the gain variation signal as a function of both a current operating temperature and a current operating frequency.

Abstract: In a feed-forward power amplifier, a main path amplifies a power level of an input signal to generate a path turning signal, an error path receives the input signal and controls a gain or a phase of a second order intermodulation component in the path turning signal to generate an intermodulation compensation signal, and a first synthesizer generates an output signal responsive to the path turning signal and the intermodulation compensation signal, achieving linearity.

Abstract: A feed-forward amplifier having a signal cancellation loop including a cancellation node that includes a gain controller and a phase controller. Each controller provides a discrete tap steering signal and modulates the corresponding tap steering signal with a discrete tracer signal that takes on a preselected sequence of values. The sequence chosen so that the tracer signal is mutually orthogonal to each other tracer signal over a preselected period. A gain and phase adjuster connected to the outputs of the controllers provides a controlled gain change and phase shift in the signal cancellation loop, the magnitude of the gain change and phase shift controlled by the corresponding tap steering signals presented to the gain and phase adjuster by the controllers. A detector, the input of which is connected to the cancellation node and the output of which is connected to the controllers, outputs a measure of the envelope of the signal at the cancellation node.

Abstract: A gain adjuster and a phase adjuster of a distortion generation path are set so that an extracted distortion component becomes small, the extracted component is compared with a reference value. When an upper-frequency distortion component of a pilot signal is larger than the reference value, the gain and phase of a frequency characteristic compensator of the distortion generation path are controlled so that the upper-frequency distortion component of the pilot signal becomes smaller than a value preset in the controller. When a lower-frequency distortion component of the pilot signal is larger than a reference value, the gain and phase of the frequency characteristic compensator of the distortion generation path are controlled so that the lower-frequency distortion component of the pilot signal becomes smaller than a value preset in the controller.

Abstract: A feed forward amplifier and method of amplification are disclosed. The amplifier output is used to generate a pilot signal via feedback using uncancelled noise in the amplifier output. An automatic level control circuit maintains the pilot signal at a substantially constant level when the detected uncancelled noise in the amplifier output is above a threshold level. The generated pilot signal strength is allowed to vary when the detected uncancelled noise in the amplifier output is below the threshold and disappears automatically when the amplifier is aligned.

Abstract: A linearizer for an amplifier includes an adaptation controller having M monitor signals as inputs. The controller outputs M control settings. The adaptation controller determines M uncorrelated adjustment settings from the M monitor signal inputs. Using the M uncorrelated adjustment settings, the controller adjusts the M control settings for the linearizer.

Abstract: A dual loop feedforward power amplifier. A dual loop feedforward power amplifier, comprising an input that provides a multicarrier signal; a first feedforward power amplifier; and a second feedforward power amplifier, wherein the first feedforward power amplifier serves as a main amplifier gain block in the second feedforward power amplifier, wherein the first feedforward power amplifier comprises a carrier cancellation loop and a first error amplifier loop, and wherein the second feedforward power amplifier comprises a third loop and a fourth loop that cancel small signal distortions that are not reduced by the first feedforward amplifier.

Abstract: A combined signal of a digital pilot signal and a digital transmission signal is applied to a digital predistorter (20), wherein it is added with odd-order distortions based on a power series model to generate a predistorted signal, then the predistorted signal is converted by a DA converter (31) to an analog signal, then the analog signal is upconverted by a frequency upconverting part (33) to a send frequency band, and the upconverted signal is output after being amplified by a power amplifier (37). A pilot signal component is extracted from the power amplifier output, then odd-order distortion components of the power series model are extracted by a digital predistorter control part (50) from the pilot signal component, and the odd-order distortions in the digital predistorter (20) are controlled to decrease the levels of the distortion components.

Abstract: A delay mismatched feed forward amplifier system employing a control system and method using floors and penalties is disclosed. The disclosed control system and method allows the second loop phase adjuster setting to be offset in a repeatable and controlled manner. Applying floors and penalties to offset the steady-state phase adjuster setting modifies the conventional pilot cancellation approach. In the conventional case, pilot cancellation has a distinct minimum that corresponds to the desired adjustment setting. In the disclosed approach, the measured pilot cancellation is clipped to a lower bound or floor to produce a set of equal valued minimum control results. The floor is selected to place a desired phase offset to the phase adjuster at the edge of minimum floor. To ensure that the correct phase adjuster offset is selected from the set of equal valued minimum control results, a control direction based penalty is added.

Abstract: A method for aligning a feed forward radio frequency power amplifier includes applying a radio frequency signal to the feed forward radio frequency power amplifier and monitoring a radio frequency signal from the feed forward radio frequency power amplifier, without opening a break point of the feed forward radio frequency amplifier.

Abstract: A pilot generation and detection system within a feed forward power amplifier that uses positive feedback to create a narrow bandwidth limit cycle is disclosed. The pilot system adjusts its frequency automatically to keep a desirable phase relationship between the pilot generation and detection. As a result, quadrature modulation/detection of the pilot used in prior approaches to ensure reliable estimates of the detected pilot power is unnecessary. This reduces the cost of the system. In addition, the pilot system turns the pilot amplitude ‘on’ or ‘off’ as needed. When the alignment of the second loop is good, the positive feedback will not have sufficient gain to maintain a limit cycle. As a result, the pilot will turn off when the second loop has converged. The pilot will return automatically as a by-product of the positive feedback if the second loop alignment degrades. Turning off the pilot when the second loop has converged reduces the pilot spurs appearing at the output of the feed forward amplifier.

Abstract: A predistortion linearizer may include a digital signal processor (DSP) for modeling a nonlinear characteristic of a high power amplifier (HPA) on a real time basis; a distortion signal generator for generating a distortion signal by using the signal modeled by the DSP; and a main path unit for combining the output signal of the HPA and the distortion signal of the distortion signal generator and transmitting an input signal without a distortion component. Since the nonlinear characteristic of the power amplifier is modeled on a real time basis to remove the distortion component contained in the output signal of the power amplifier, the nonlinear characteristic of the power amplifier is improved, and thus, an efficiency of the power amplifier can be maximized.

Abstract: A circuit is provided, having a feed forward linear power amplifier configured with two or more error correction loops (225–235, 255–265). Each of the error correction loops includes a band pass filter (237, 257). Each of the band pass filters (237, 257) is tuned to a different frequency range. A controllable frequency oscillator (220) can be coupled to an input of the error correction loops. A controller sweeps the frequency of the controllable frequency oscillator over the frequency range corresponding to each of the band pass filters (237, 257).

Abstract: An amplifier linearizer includes a signal adjuster having an internal signal, and an adaptation controller for monitoring the signal adjuster. The internal signal at an input to the adaptation controller is deemed a monitor signal. The adaptation controller generates a control signal for the signal adjuster by accounting for a difference between the internal and monitor signals.

Abstract: The present invention provides a novel feed forward amplifier (“FFA”) and a pilot tone generator-receiver therefor. In an embodiment of the invention, the feed forward amplifier only requires a single oscillator to operate both the pilot tone generator and pilot tone receiver used in conjunction with the amplifier circuitry of the FFA. In another embodiment of the invention, a method is provided of generating and detecting a pilot tone from a single oscillating signal.

Abstract: A transmission signal and a pilot signal are predistorted by a digital predistorter 13 by use of a power-series model, and the predistorted output is converted by a digital-analog converter 14 to an analog signal. The analog signal is up converted by a frequency converter 15 to an RF-band signal, which is transmitted after being power-amplified by a Doherty amplifier 16. The pilot signal is extracted by a pilot signal extractor 17 from the output from the Doherty amplifier, and the extracted pilot signal is down converted by a frequency converter 18 to a baseband signal. The baseband pilot signal is converted by an analog-digital converter 19 to a digital pilot signal. A control part 21 detects an odd-order distortion component from the digital pilot signal, and based on the detected result, controls parameters of the digital predistorter.

Abstract: A control system comprising an electrical circuit that produces distortion where the electrical circuit has a frequency band of operation. A pilot modulated carrier signal is frequency hopped about the frequency band of operation. The hopping pilot modulated carrier signal does not interfere with any signal applied to or generated by the electrical circuit as it is not at any time located within the frequency band of operation. Information obtained from the hopping pilot modulated carrier is provided to the control system which uses such information to cancel the distortion produced by the electrical circuit.

Abstract: Procedures for decorrelating the branch signals of a signal adjuster of an amplifier linearizer are presented herein. The decorrelation procedures can be performed with or without self-calibration.