Abstract: Briefly, an apparatus having an outphasing modulator that may provide at least first and second outphased signals to a power amplifier. The outphasing modulator may control amplitude of the first and second outphased signals by an amplitude modulation controller which may vary an amplitude level of first and second control signals base on a desired output power level of said power amplifier.

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 feed forward amplifier employing a new adaptive controller and method is disclosed. The controller aligns both a gain adjuster and phase adjuster of a first cancellation loop. The phase adjuster may be controlled following a standard approach. However, the gain adjuster is offset intentionally causing an incomplete cancellation, increasing the signal power passing through the error amplifier. If the gain adjuster is offset low, below the gain adjustment required to maximize carrier cancellation, peak power output from the main amplifier is reduced while the second loop maintains constant system output power. If the gain adjuster is offset high, peak power output from the error amplifier is reduced while the second loop maintains constant system output power. By controlling the gain adjuster offset from full first loop cancellation, the feed forward amplifier can be optimized for the power handling capabilities of the main and error amplifiers.

Abstract: A feedforward amplifier. The present invention therefore provides a feedforward amplifier, comprising: a pilot reference generator that generates a pilot signal; a first carrier cancellation loop; a first error amplifier loop including a first error amplifier, wherein the pilot signal is utilized to provide gain stabilization in the first error amplifier a third loop; a second carrier cancellation loop that includes a first phase and amplitude adjuster in module and a second amplitude and phase adjuster disposed between module and module, wherein the pilot signal is utilized to control the adjustment of the second carrier cancellation loop.

Abstract: A system and method of pilot tone reuse.

Abstract: The invention provides robust and non-invasive calibration of an adaptive signal conditioning system having a signal conditioning block in the signal path to a signal conversion system, and a feedback path with a number of feedback components for enabling adaptation, by means of a parameter adaptation block, of the parameters used in the signal conditioning. In order to calibrate the feedback path, a well-defined reference signal is inserted into the feedback path, and an appropriate calibration coefficient is then determined by a coefficient calibrator in response to the received reference signal. The calibration coefficient is provided to a compensator, which effectively compensates for changes in the transfer characteristics of the feedback path due to factors such as variations in ambient temperature and component aging.

Abstract: The conventional feedforward amplifier is unable to suppress distortion components efficiently. The present invention provides a feedforward amplifier wherein the vector adjustor is adjusted so that (1) suppression is performed on only the distortion component generated within a predetermined frequency range out of the range of frequencies to be suppressed in which distortion components to be suppressed occur or (2) the suppression of the distortion component generated within the predetermined frequency range is greater than the suppression of the distortion component generated within the frequency range other than the predetermined frequency range out of the range of frequencies to be suppressed, and the pre-distortion circuit is adjusted so that at least the distortion component generated within the frequency range other than the predetermined frequency range is suppressed.

Abstract: An amplifier arrangement including a main amplifier to which feed-forward cancellation is applied, where the amplifier arrangement comprises an input for receiving signals to be amplified, an output for providing an amplified input signal, a pilot signal modulation circuit to generate a CW frequency shifted pilot signal, a mixer down for converting the pilot signal to an IF signal, and a sampling circuit for digitally sampling the IF signal. The amplifier arrangement includes a signal cancellation loop and a distortion cancellation loop each acting as an independent control function for minimizing pilot signal. The signal cancellation loop utilizes a Cartesian loop method for controlling the signal cancellation loop for sensing both phase and amplitude information simultaneously. The Cartesian loop uses a high frequency active mixer, which is a dual cross coupled differential pairs of devices capable of operating with input signals from near DC to 2.4 GHz, for control of the signal cancellation loop.

Abstract: In a multicarrier amplifying device, a power detecting section of a variable frequency type changes a detection frequency according to a carrier frequency, a power of which is to be measured, to detect a power level of each carrier, and a controlling section automatically adjusts the power level of the carrier on the basis of the detected power level. It is possible to automatically set a transmission power level of one carrier to a specified power level without stopping existing carriers.

Abstract: In a feedforward amplifier with a dual loop in which a distortion injection path of a distortion elimination circuit 50 is provided as a feedforward configuration composed of a first auxiliary amplifier distortion elimination circuit 60 and a first auxiliary amplifier distortion elimination circuit, a second variable attenuator 55 and a second variable phase shifter 56 are provided preceding the distortion detection circuit 60, a second pilot signal injected between stages of a main amplifier 14 is detected by a directional coupler 85, and the second variable attenuator 55 and the second variable phase shifter 56 are controlled by a second controller 97 to minimize the level of the detected second pilot signal, thereby bringing the distortion elimination circuit and the first auxiliary distortion detection circuit into balance at the same time.

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.

Abstract: The object of this invention is to provide a feedforward amplifier that performs precise distortion compensation on a plurality of signal groups without adopting broadband frequency-band characteristics for the auxiliary amplifier. This is achieved by inputting a plurality of signal groups, each having a different frequency bandwidth respectively. In a distortion detection loop, a main amplifier 4 is used to amplify this plurality of input signal groups and detect the distortion arising in said main amplifier 4. In a distortion compensation loop the distortion detected in the distortion detection loop is removed from the amplified signal from said main amplifier 4.

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 feed forward RF power amplifier which provides both high efficiency and minimal distortion in broad bandwidth RF applications. The feed forward power amplifier includes a main amplifier biased to provide high efficiency and an error amplifier biased to provide highly linear operation through substantially the entire operating range. Signal peaks which introduce distortion components at the main amplifier output are cancelled by the linear operation of the error amplifier.

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: The present invention is intended to provide a feedforward amplifier circuitry which is capable of changing a location or placement of each section constituting the feedforward circuitry, in particular a feedforward amplifier circuitry which is capable of changing an interposing location of a variable phase shifter. In the feedforward amplifier circuitry, a variable phase shifters (5, 12) can be disposed on a location other than a post-stage of a predistortion circuits (3, 20), as a result of which it is advantageously possible to provide a designer with more flexibility in changing the locations of variable shifters, regardless of the conventional arrangement of the variable phase shifters disposed on the post-stages of the distortion circuits, when the feedforward amplifier is actually designed.

Abstract: The present invention relates to a Multi Carrier Power Amplifier, MPCA, comprising a number of parallel Multi Carrier Power Amplifiers, each comprising an amplification loop and an error cancellation loop, said amplification loop comprising at least a first gain and phase control network and a first amplifier and a second amplifier. The MPCA comprises an external loop comprising a second Spread Spectrum Signal added to said each first loop.

Abstract: A method of controlling a feedforward distortion compensation amplifier has steps of detecting a distortion component generated in a main amplifier by coupling a signal branched from a signal input to the main amplifier and containing a plurality of carriers of different frequencies to a signal branched from an output signal from the main amplifier so that the coupling causes the carrier components to cancel each other, recoupling the signal resulting from the coupling to the output signal from the main amplifier, and adjusting an amplitude and phase of at least one of the signals to be recoupled so that distortion components cancel each other upon recoupling, wherein a first and second pilot signals obtained from a first and second pilot signal sources are inserted into the input signal to or output signal from the main amplifier, parts of the signal resulting from the recoupling are taken out through branching, and the signals taken out through branching are mixed with the first and second pilot signals

Abstract: A feedforward amplifier includes a main amplifier for amplifying an input signal, a control circuit for generating a predetermined pilot signal based on the output of a local oscillator and a frequency divider included in the control circuit, and a coupler for combining the input signal or the amplified signal with the pilot signal to generate a combined signal. A first coupler and a second coupler are provided for extracting any distortion component from the combined signal. A vector adjuster, an error amplifier, and a third coupler are provided for removing the extracted distortion component from the combined signal to generate an output signal. An orthogonal detector is provided for using any one of the pilot signal, or the output of the local oscillator, the frequency divider, and the combination of the vector adjuster, error amplifier, and the third coupler to make an adjustment for removing the distortion component.

Abstract: A method and apparatus for utilizing the distortion generated within a portion of a balanced amplifier to cancel the distortion generated within the whole balanced amplifier. Samples of the signal and distortion from part of the balanced amplifier are combined with a reference signal such that the two signals destructively combine leaving the distortion from the sampled part of the balanced amplifier. The gain and phase of the distortion is then adjusted so that when it is coupled into the input of the other part of the balanced amplifier the distortion generated by both parts of the balanced amplifier are cancelled.

Abstract: A feed forward amplifier performs a carrier cancellation tuning process separate from an IM reduction tuning process, wherein the carrier cancellation tuning process is performed without reference modulations that are utilized to modulate a feed forward amplifier input signal during the IM reduction tuning process. By decoupling the reference modulations during the carrier cancellation process, the feed forward amplifier is able to eliminate the instantaneous carrier cancellation degradation that would otherwise be caused by the reference modulations.

Abstract: The object of this invention is to provide a feedforward amplifier that performs precise distortion compensation on a plurality of signal groups without adopting broadband frequency-band characteristics for the auxiliary amplifier. This is achieved by inputting a plurality of signal groups, each having a different frequency bandwidth respectively. In a distortion detection loop, a main amplifier 4 is used to amplify this plurality of input signal groups and detect the distortion arising in said main amplifier 4. In a distortion compensation loop the distortion detected in the distortion detection loop is removed from the amplified signal from said main amplifier 4.

Abstract: An amplifier linearizer circuit has a signal cancellation circuit including a signal adjuster having M branch signals (M≧1), and a distortion cancellation circuit including a signal adjuster having N branch signals (N≧1). The linearizer has a controller for adaptively controlling the M-branch and N-branch signal adjusters. The controller has only one monitor receiver to monitor the M branch signals and only one monitor receiver to monitor the N branch signals.

Abstract: An RF power amplifier with amplifier stage failure detection comprises an amplifier input for receiving an RF signal to be amplified, an amplifier output for outputting an amplified RF signal, a plurality of separate amplifier stages coupled between the amplifier input and amplifier output so as to cumulatively provide a desired amplifier gain to the input RF signal, and means for detecting amplifier stage failure by providing a pilot tone separately to the amplifier stages based on a separate timing for each stage and detecting pilot tones output from the stages based on the timing.

Abstract: An amplifier distortion reduction system detects a plurality of amplitudes corresponding in time within a frequency band of operation. In response to at least one of the plurality of amplitudes, adjustments can be made to components within the frequency band of operation, enabling the amplifier distortion reduction system to adapt to changing operating conditions. In a feed forward embodiment having a carrier cancellation loop and IMD cancellation or distortion cancellation loop, the output of the carrier cancellation loop can be monitored and equalizer adjustments provided to reduce the amplitude of the carrier signal(s) equally over the frequency band of operation. The output of the IMD cancellation loop can be monitored and equalizer adjustments provided to reduce the IMD components equally over the frequency band of operation. Thus, processing circuitry can monitor amplitudes corresponding in time over the frequency band of operation and provide improved performance over the frequency band.

Abstract: The present invention is intended to provide a feedforward amplifier circuitry which is capable of changing a location or placement of each section constituting the feedforward circuitry, in particular a feedforward amplifier circuitry which is capable of changing an interposing location of a variable phase shifter. In the feedforward amplifier circuitry, a variable phase shifters (5, 12) can be disposed on a location other than a post-stage of a predistortion circuits (3, 20), as a result of which it is advantageously possible to provide a designer with more flexibility in changing the locations of variable shifters, regardless of the conventional arrangement of the variable phase shifters disposed on the post-stages of the distortion circuits, when the feedforward amplifier is actually designed.

Abstract: An apparatus and method for operating an adaptive circuit includes injecting a set of orthogonal tracer signals into the circuit. The tracers signals are extracted after modification by at least a portion of the circuit and are examined by respective controllers to modify operation of the circuit. In one embodiment, the invention is incorporated into a feed forward amplifier where a set of orthogonal tracer signals are injected into the amplifier. A detector controller detects the orthogonal tracer signals, as modified by portions of the amplifier, and applies each tracer signal to a respective controller. Each controller examines its respective signal and modifies its output to control a portion of the amplifier accordingly. The controllers apply their outputs to the respective portions of the amplifier at substantially the same time, leading to quick convergence of the operating point of the amplifier to an optimal or near-optimal configuration.

Abstract: A distortion reduction system uses upstream signal information, such as the carrier frequencies in an input signal, to adjust at least one frequency for a pilot signal to be injected into the distortion reduction system and to be detected at the output of the distortion reduction system, thereby enabling improved distortion reduction of changing input signals. For example, processing circuitry obtains the traffic frequencies making up a signal to be amplified by a feed forward arrangement. Using the traffic frequencies, the processing circuitry determines at least one frequency for a pilot signal, and the processing circuitry tunes a pilot signal generator to the at least one frequency for the pilot signal. The feed forward arrangement receives the signal to be amplified and provides replicas of the signal on a main signal path and on a feed forward path. The pilot signal is injected into the main signal path at the at least one frequency along with the signal to be amplified.

Abstract: A method of setting up a linearizing circuit such as a linear power amplifier is described. According to the method, an input signal is supplied at a low, starting power level and is lowly increased during a set-up until it attains an operational level for normal use. The advantage of this is that pilot tone used in the linearizing circuit can be readily detected during set-up because its amplitude is above that of the low, starting power level of the input signal. A feed-forward linearizing system and a transmission system utilizing the technique are described.

Abstract: An RF power amplifier with amplifier stage failure detection comprises an amplifier input for receiving an RF signal to be amplified, an amplifier output for outputting an amplified RF signal, a plurality of separate amplifier stages coupled between the amplifier input and amplifier output so as to cumulatively provide a desired amplifier gain to the input RF signal, and means for detecting amplifier stage failure by providing a pilot tone separately to the amplifier stages based on a separate timing for each stage and detecting pilot tones output from the stages based on the timing.

Abstract: The predistortion circuit (200) predistorts the input signal to a non-linear signal processing device in order to linearise its output. The predistortion circuit (200) derives the predistortion by sampling the input at (210) and multiplies it with itself using mixers (multipliers) (220, 226, 230, 236, etc.) in order to generate various orders of distortion (212, 214, etc.) which are summed to provide the predistortion. Filter/time delay means (240, 242, 244) are incorporated in the paths which generate the orders of distortion in order to introduce a phase and/or amplitude variation with frequency into the distortion. The filter/time delay means can be implemented by adaptive filters in digital signal processing circuits (DSPs). The DSPs can sample the output of the signal processing device being linearised in order to obtain feedback for adapting the filter(s).

Abstract: A feedforward amplifier combines an input signal combined by a first error rejection loop with an error component and a first pilot signal detected by a second error detection loop, thereby canceling out the error component and the first pilot signal residual in the input signal.

Abstract: In a multicarrier amplifying device, a power detecting section of a variable frequency type changes a detection frequency according to a carrier frequency, a power of which is to be measured, to detect a power level of each carrier, and a controlling section automatically adjusts the power level of the carrier on the basis of the detected power level. It is possible to automatically set a transmission power level of one carrier to a specified power level without stopping existing carriers, and without using an expensive spectrum analyzer or the like, which provides a great merit in operation, and is helpful to reduce labor in maintaining and checking works.

Abstract: In a feedforward amplifier with a dual loop in which a distortion injection path of a distortion elimination circuit 50 is provided as a feedforward configuration composed of a first auxiliary amplifier distortion elimination circuit 60 and a first auxiliary amplifier distortion elimination circuit, a second variable attenuator 55 and a second variable phase shifter 56 are provided preceding the distortion detection circuit 60, a second pilot signal injected between stages of a main amplifier 14 is detected by a directional coupler 85, and the second variable attenuator 55 and the second variable phase shifter 56 are controlled by a second controller 97 to minimize the level of the detected second pilot signal, thereby bringing the distortion elimination circuit and the first auxiliary distortion detection circuit into balance at the same time.

Abstract: An RF power amplifier with amplifier stage failure detection comprises an amplifier input for receiving an RF signal to be amplified, an amplifier output for outputting an amplified RF signal, a plurality of separate amplifier stages coupled between the amplifier input and amplifier output so as to cumulatively provide a desired amplifier gain to the input RF signal, and means for detecting amplifier stage failure by providing a pilot tone to the amplifier stages, duty cycling the amplifier stages based on a separate timing for each stage and detecting the pilot tone output from the stages based on the timing.

Abstract: The present invention relates to a linear amplifier for amplifying power of a radio-frequency signal whose level varies widely, based on feed-forward technique. The linear amplifier according to the present invention is given in advance appropriate transfer characteristics for an error elimination loop and an error detection loop and these appropriate transfer characteristics are applied at a starting time. Therefore, performance and total reliability of equipment to which the present invention is applied are enhanced and cost reduction thereof is realized.

Abstract: A pilot adjusting system adjusts the power level of the pilot relative to the power level of the input signal. For example, the pilot adjusting system detects the power level of the input signal on the signal path leading to an RF amplifier. In response to the power level of the input signal, the pilot adjusting system adjusts the power level of the pilot signal which is injected into the signal path prior to the RF amplifier. In certain embodiments, the pilot adjuster adjusts the pilot power level to maintain a desired input signal to pilot signal ratio at the input to the RF amplifier for the input signal range of the RF amplifier. As such, if the input signal power level drops 30 dB, the pilot adjuster reduces the power level of the pilot signal by 30 dB, thereby maintaining the input signal to pilot ratio throughout the input range of the RF amplifier.

Abstract: The digital transmission sub-system comprises a DSP (100) which takes as its inputs the in-phase and quadrature channels of a baseband software radio stage. The in-phase and quadrature inputs are separately digitally predistorted (110, 120) and digitally up-converted (128) to the intermediate frequency (IF) band. The IF band signal is then converted (130) to an analogue signal which is up-converted to the radio frequency band at (134) prior to amplification at (140) to produce an RF output signal for radiation from an antenna. The predistors (110 and 120) predistort the incoming signals to counter distortion arising from the up-conversion and amplification processes within the transmission subsystem in order to linearise the RF output. The predistorters (110, 120) may be adapted using a feedback signal supplied to the DSP (100) from a splitter (142) at the output of the sub-system.

Abstract: A feedforward amplifier has

Abstract: A distortion compensation amplifier has a distortion detection loop that divides an input signal, amplifies one divided signal with an amplifier and uses the amplified signal and another divided signal to detect a distortion component generated and introduced into the amplified signal in the amplifier and a distortion removal loop that removes the detected distortion component from the amplified signal produced by the amplifier. The distortion detection loop comprises filter means for reducing the distortion component of the amplified signal output by the amplifier that was generated and introduced into the amplified signal in the amplifier and detects the distortion component reduced by the filter means. The distortion removal loop removes from the amplified signal the detected distortion component that was produced by the amplifier and reduced by the filter means.

Abstract: A feedforward amplifier is linearized by adapting off the detection of an applied modulation source. The feedforward amplifier has two loops: a first loop and a second loop. Modulators in the two loops are adjusted by controllers that adapt in response to detection of the modulation source injected into the first loop.

Abstract: An apparatus and method for operating an adaptive circuit includes injecting a set of orthogonal tracer signals into the circuit. The tracers signals are extracted after modification by at least a portion of the circuit and are examined by respective controllers to modify operation of the circuit. In one embodiment, the invention is incorporated into a feed forward amplifier where a set of orthogonal tracer signals are injected into the amplifier. A detector controller detects the orthogonal tracer signals, as modified by portions of the amplifier, and applies each tracer signal to a respective controller. Each controller examines its respective signal and modifies its output to control a portion of the amplifier accordingly. The controllers apply their outputs to the respective portions of the amplifier at substantially the same time, leading to quick convergence of the operating point of the amplifier to an optimal or near-optimal configuration.

Abstract: An amplifier linearizer circuit has a signal cancellation circuit including a signal adjuster having M branch signals (M≧1), and a distortion cancellation circuit including a signal adjuster having N branch signals (N≧1). The linearizer has a controller for adaptively controlling the M-branch and N-branch signal adjusters. The controller has only one monitor receiver to monitor the M branch signals and only one monitor receiver to monitor the N branch signals.

Abstract: A method of controlling a feedforward distortion compensation amplifier has steps of

Abstract: A hybrid multicarrier RF power amplifier linearization architecture combines ACT and feed-forward amplifier stages to achieve high output distortion rejection and enhanced amplifier linearity. A carrier cancellation loop is coupled with a main RF power amplifier stage having parallel RF power amplifiers coupled via intermod-complementing predistortion paths. The carrier cancellation loop is coupled to a feed-forward loop containing a feed-forward RF power amplifier, to produce a composite amplified output signal having very reduced intermodulation products. Vector modulators in the main amplifier and feed-forward amplifier stages are controlled by a digital signal processor, using outputs from various monitoring subsystems, including pilot tone detection, correlator, distortion and power detector circuits.

Abstract: A method and apparatus for utilizing the distortion generated within a portion of a balanced amplifier to cancel the distortion generated within the whole balanced amplifier. Samples of the signal and distortion from part of the balanced amplifier are combined with a reference signal such that the two signals destructively combine leaving the distortion from the sampled part of the balanced amplifier. The gain and phase of the distortion is then adjusted so that when it is coupled into the input of the other part of the balanced amplifier the distortion generated by both parts of the balanced amplifier are cancelled.

Abstract: A predistortion system uses a pilot signal to determine a predistortion function which is used to produce amplitude and/or phase adjustment(s) of an input signal on a signal path. Rather than simply detecting the input signal envelope before and after distortion generating circuitry, such as an amplifier, a pilot signal is provided on the signal path prior to the distortion generating circuitry. After the distortion generating circuitry, the pilot signal is detected. The predistortion system can determine the predistortion function by using the generated pilot signal and the detected pilot signal, for example, to provide improved characterization of the amplifier amplitude and/or phase response or to directly improve the determination of the predistortion function.

Abstract: A feed-forward amplifier and a controller thereof. Two types of second pilot signals, sum frequency and difference frequency of a base pilot signal and a local oscillation signal, are generated by an injection-side mixer and injected into a distortion detection loop. Part of a signal appearing at an output terminal is branched, converted in frequency by a detection-side mixer using the local oscillation signal, filtered by a narrow-band filter, input to a synchronizing detector with the filtered output of the filter as error signals, and synchronizing detected with reference to the base pilot signal so as to generate control signals for a distortion rejection loop. The spectrums of the second pilot signals may be spread. A process to cancel the input signal component at the detection side may be performed. A simple circuit configuration enhances the distortion component rejection and suppression effect and shortens the time required until an optimum control state is established.

Abstract: The present invention relates to a linear amplifier for amplifying power of a radio-frequency signal whose level varies widely, based on feed-forward technique. The linear amplifier according to the present invention is given in advance appropriate transfer characteristics for an error elimination loop and an error detection loop and these appropriate transfer characteristics are applied at a starting time. Therefore, performance and total reliability of equipment to which the present invention is applied are enhanced and cost reduction thereof is realized.

Abstract: A feedforward amplifier combines an input signal delayed by a delay circuit with an output signal by a combiner; down-converts the output of the combiner to a low frequency by a frequency converter; extracts a distortion component from the output of the frequency converter; measures the distortion component by a power detector; and controls a second vector regulator of a distortion canceling loop by a controller such that the distortion component measured becomes minimum.