Abstract: A signal is predistorted by producing a first set of sample values using a first predistortion technique, producing a second set of sample values using a second predistortion technique different than the first predistortion technique, and combining the first and second sets of sample values to produce a predistorted signal. At least one of the first and second predistortion techniques produce the corresponding set of sample values based at least in part on a plurality of past time spaced input samples relative to a current time spaced input sample.

Abstract: A group delay adjusting circuit. The group delay adjusting circuit comprises an electronically adjustable variable capacitance, and an electronically variable virtual inductor coupled in parallel to the electronically variable capacitance at a node.

Abstract: (Object) It was difficult for a feedforward amplifier to perform stable and high-speed distortion compensation control. (Constitution) It is a feedforward amplifier having CPL1 of dividing an input carrier signal into two output signals, VAP1 of adjusting one of the two divided output signals, AMP1 of amplifying the adjusted one of the output signals to generate an amplification signal, CPL2 of extracting a distortion signal by utilizing the other output signal of the two divided output signals and the generated amplification signal, CPL3 of generating an output carrier signal by utilizing the generated amplification signal and the extracted distortion signal, and CNT1 having a log amplifier of controlling VAP1 based on the other output signal and the generated amplification signal.

Abstract: A feedforward amplifier, and a method of improving the performance thereof, are provided. More particularly, a feedforward amplifier using imperfect cancellation of a main signal and a method of improving the performance thereof, in which, by including a predetermined amount of a main signal in an error signal that is input to an error signal cancellation loop of the feedforward amplifier, more error components of a final output signal are removed, such that the linearity and efficiency of the final output signal improve.

Abstract: An amplifier architecture using actively phase-matched feed-forward linearization includes: a first signal path having a scaling amplifier 40 in series with a main amplifier 42; a second signal path having a replica amplifier 44 in series with a correction amplifier 46; and a combining node 48 that combines the first signal path and the second signal path. This topology places the scaling amplifier 40 in the main signal path. By inverting the scaling factor from &bgr; to 1/&bgr;, this topology retains the distortion cancellation property while balancing the two signal paths. In this case the scaling amplifier 40 attenuates the input signal rather than amplifying it. The end result remains the same. The main amplifier output signal is lower than the replica amplifier's by a factor of &bgr;. This results in a third-order distortion component that is &bgr;3 times bigger at the replica amplifier output.

Abstract: A feedforward amplifier is disclosed in which either the main amplifier or the auxiliary amplifier includes at least three parallel signal paths. Each of the signal paths includes a complex gain adjuster. In addition, a feedforward amplifier is disclosed in which a plurality of control linearizers compensate for nonlinearities in the response of signal adjusters to control inputs.

Abstract: A feed forward power amplifier is disclosed which utilizes three signal cancellation loops. Loop 1 includes a main amplifier and is used to derive a carrier cancelled sample of the main amplifier output. Loop 2 includes an error amplifier used to amplify the carrier cancelled signal derived from Loop 1 operation in order to cancel distortion products generated due to the nonlinear nature of the main amplifier. Loop 2 also utilizes a very short Loop 2 delay line. A significant efficiency gain is provided due to reduced output power losses associated with the Loop 2 delay line. Lower output losses also results in lower distortion levels produced by the main amplifier. This, in turn, reduces the size and performance requirements placed on the error amplifier. A smaller and more efficient error amplifier is employed resulting in further amplifier system efficiency improvement.

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: Signal handling equipment, such as a high power amplifier, is implemented with feed-forward compensation circuitry that adjusts the effective operation of the equipment (e.g., linearizes the amplifier). The compensation circuitry includes (i) a nulling loop, which generates an error signal based on the output from the amplifier, and (ii) an error loop, which generates, based on the error signal, a feed-forward compensation signal that is added to the output of the amplifier. The compensation circuitry is tuned by tuning the nulling loop and then iteratively tuning the error loop based on data generated by perturbing the tuning of the nulling loop. In one implementation, data corresponding to the amplitude of the output signal is analyzed to generate metric values that are used to iteratively adjust the tuning of the error loop.

Abstract: An impedance matching low noise amplifier (“LNA”) having a bypass switch includes an amplification circuit, a bypass switching network and a match adjustment circuit. The amplification circuit has an amplifier input and an amplifier output, and is configured to receive a radio frequency (RF) input signal at the amplifier input and apply a gain to generate an amplified RF output signal at the amplifier output. The bypass switching network is coupled to a low-gain control signal and is also coupled between the amplifier input and the amplifier output. The bypass switching network is configured to couple the amplifier input to the amplifier output when the low-gain control signal is enabled in order to feed the RF input signal through to the RF output signal. The match adjustment circuit is coupled to the low-gain control signal and the RF input signal, and is configured to couple the RF input signal to an impedance when the low-gain control signal is enabled.

Abstract: The signal generated by a high-power amplifier (HPA) operating in its non-linear region is linearized by an amplifier circuit using feed-forward compensation in which an auxiliary channel relies on a model of the HPA to generate an auxiliary signal that is combined with the HPA output to generate an amplified linearized output signal. The amplifier circuit may be implemented with a pre-distorter in the main amplifier channel to linearize the HPA using both pre-compensation and feed-forward compensation. Using the HPA model in the auxiliary channel enables the auxiliary signal to be generated without directly relying on the HPA output. This enables the amplifier circuit to be implemented without having to delay the high-power HPA output signal prior to being synchronously combined with the auxiliary signal. In preferred embodiments, the auxiliary channel signal is generated using a relatively low-power amplifier operating in its linear region.

Abstract: A power feedforward amplifier uses integral cavities to provide RF isolation between subcircuits of the power amplifier. The chassis includes a main chassis body and a lid structure adapted to couple with the chassis body and define the subcircuit cavities. The inner lid includes an amplifier dividing wall and interstage walls adapted to isolate the main and error amplifier subcircuits of the feedforward power amplifier and further to isolate individual components of the subcircuits. In one embodiment, the amplifier subcircuits are mounted on a single circuit board and isolated from each other by the dividing wall. A delay line subcircuit portion is integral with the main chassis body and is coupled beneath the error amplifier subcircuit to contain and electromagnetically shield a delay line filter subcircuit while providing direct connection with the error 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: The present invention is a variable gain amplifier for amplifying a radio frequency signal by using a field effect transistor for signal amplification. The variable gain amplifier includes: an input impedance correcting means for correcting the input impedance when varying the gain at the input side of the field effect transistor for signal amplification; an output impedance correcting means for correcting the output impedance when varying the gain at the output side of the field effect transistor for signal amplification; and an amplifier bypass means for passing the radio frequency input signal to the output side by skipping the field effect transistor for signal amplification when varying the gain. According to the present invention, a variable gain amplifier is favorable in the voltage standing wave ratio (VSWR) at the input and output end regardless of presence or absence of gain variation, and the gain attenuation amount can be arbitrarily set.

Abstract: In an adaptive predistorter type distortion compensating apparatus for calculating a distortion compensating coefficient by using an adaptive algorithm so as to reduce an error between a reference signal and a feedback signal of a circuit which generates a distortion on the basis of the reference signal, and for compensating the distortion by providing the distortion compensating coefficient to the reference signal, a phase adjustment circuit is provided for determining a phase shift value which reduces a phase difference between a reference signal and a feedback signal, for correcting the phase of the reference signal or the feedback signal by the phase shift value, and for calculating the distortion compensating apparatus after the correction.

Abstract: A feed forward type distortion compensation amplification apparatus, which includes a distortion detection loop and a distortion compensation loop, cancels a first distortion element generated from the distortion detection loop by a second distortion element generated from the distortion compensation loop to generate an output signal, and controls bias levels of the main amplifier and the error amplifier based on a level of the output signal. An adaptive pre-distortion type distortion compensation amplification apparatus includes a detection unit for detecting an input power level, a control unit for storing the input power level and a bias level corresponding thereto and generating the bias level in response to the input power level, and a bias control unit for applying a bias to an amplifier unit in response to the bias level.

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 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: 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 transmitter includes a feed forward amplifier that includes main signal path having a radio frequency (RF) power amplifier, a feed forward correction circuit, and a control circuit. An amplification of an input signal by the RF power amplifier produces an amplified signal that includes a distortion component. The feed forward correction circuit produces an error signal, which error signal is used to drive an error amplifier to produce an amplified error signal. In order to minimize a distortion component introduced to the amplified error signal by the error amplifier, the control circuit controls a peak power of the error signal based on a detected energy of an attenuated version of the error signal or based on the distortion component introduced to the amplified error signal by the error amplifier.

Abstract: Disclosed is a transmission amplifier having a distortion compensator for compensating for distortion of an amplifier; an amplifier for amplifying the transmit signal that has undergone distortion compensation; a feedback unit for feeding an output signal from the amplifier back to the distortion compensator; and a delay circuit for inputting the transmit signal to the distortion compensator upon delaying the transmit signal for a delay time equivalent to time required for the feedback signal to arrive at the distortion compensator. A delay time TDS of the feedback signal at the time of stand-alone operation of the transmission amplifier and a delay time difference &Dgr;T between delay times of the feedback signal at the time of stand-alone operation and at the time of parallel operation are stored in advance. The delay time TDS is set in the delay circuit at the time of stand-alone operation, and (TDS+&Dgr;T) is set in the delay circuit at the time of parallel operation.

Abstract: According to a digital linearizing method, a digital input signal on a first path is operated with an output signal of a main amplifying unit, to thus detect distortion components included in the output signal of the main amplifying unit. A digital input signal on a second path is correlated with the detected distortion components, to thus adaptively control a gain of the digital input signal on the second path during the detection of the distortion components. Therefore, according to the above method, it is possible to effectively and correctly remove the distortion components included in the output signal of the main amplifying unit by amplifying the detected distortion components and coupling the amplified distortion components with the output signal of the main amplifying unit.

Abstract: A novel linearization apparatus for reducing power amplifier distortion does not require delay lines. The apparatus includes a power amplifier and an error generator. The signals provided by the error generator (error signal) and the power amplifier are combined to subtract out the distortion introduced by the power amplifier. The error generator includes two auxiliary amplifiers, wherein one of the auxiliary amplifiers is operated in it saturated region and the other is operated in its non-saturated region. The power amplifier and the two auxiliary amplifiers have the same distortion characteristics and receive the same input signal. The auxiliary amplifier operating in its saturated region introduces distortion and the auxiliary amplifier operating in its non-saturated region does not introduce distortion. The two signals provided by the auxiliary amplifiers are combined to produce an error signal having a distortion component that is an approximate replica of the power amplifier distortion.

Abstract: A feedforward amplifier is disclosed in which either the main amplifier or the auxiliary amplifier includes at least three parallel signal paths. Each of the signal paths includes a complex gain adjuster. In addition, a feedforward amplifier is disclosed in which a plurality of control linearizers compensate for nonlinearities in the response of signal adjusters to control inputs.

Abstract: An amplifier system (120) for radio frequency signals comprises a combination of a phase and gain adjuster (122) and a first amplifier (123) which receives an input signal and generates a first amplified signal having a gain adjusted in accordance with a gain of the phase and gain adjuster. A main amplifier (126) receives the first amplified signal and generates a second amplified signal. A first controller (134) uses a signal derived from the second amplified signal to generate a first control signal. The first control signal is applied to the phase and gain adjuster to control the gain of the phase and gain adjuster. A second controller (170) is connected to receive the first control signal and to generate a second control signal which is applied to the first amplifier. The second control signal is generated to control the first control signal and thereby control noise of the amplifier system.

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: An amplifier that accurately amplifies signals over a wide bandwidth, including DC, has a voltage-to-current converter, a feed-forward resistive element, a buffer, an input resistive element, a feedback resistive element, and an operational amplifier. A first end of the feed-forward resistive element is coupled to an output of the voltage-to-current converter and to an input of the buffer. A first end of the input resistive element is coupled to an input to the voltage-to-current converter. A first end of the feedback resistive element is coupled to an output of the buffer. An inverting input of the operational amplifier is coupled to a second end of the input resistive element and to a second end of the feedback resistive element. A noninverting input of the operational amplifier is coupled to ground, and an output of the operational amplifier is coupled to a second end of the feed-forward resistive element.

Abstract: The present invention relates generally to the problem of linearization in electronic amplifiers, and more particularly to the problem of controlling phase shift in these systems. The invention measures the outgoing phase difference, directly or indirectly, and then rotates the Cartesian system accordingly to adjust the phase error in the system to within a few degrees. The phase difference can be measured in different places in the system as can the performance of the Cartesian rotation. The rotation is necessary to make the system unconditionally stable independent of the phase difference between the main amplifier path and the reference path. The invention achieves stabilization of the phase in a power amplifier, thereby eliminating the need for time-consuming adjustments and also allows the achievement of higher bandwidths since the phase control is very accurate.

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. The amplifier additionally has a distortion removal loop that removes the detected distortion component from the amplified signal produced by the amplifier. The distortion detection loop comprises a filter 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. The distortion removal loop removes from the amplified signal the detected distortion component that was produced by the amplifier and reduced by the filter.

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: The design and performance of an analog cancellation system is presented. The system generates either narrow or wideband nulls in order to minimize the effect of interfering signals on a receiver. A microcontroller directs the detection and classification of the interfering signal relative to frequency, amplitude and modulation, such as pulse-width or continuous wave modulation. A sampled version of the interfering signal at frequency, fi, is phase-inverted, amplified, and vector-summed with the input signal stream to null the interfering signal at fi. The microcontroller also monitors and adjusts the cancellation systems' circuit parameters to minimize any residual interfering signal at fi or respond to changes in the interference. The example system operates from 100-160 MHz, and can generate wideband nulls over a 5MHz bandwidth with a 15dB depth attenuation or narrowband nulls with a Q greater than 200, and with a null depth greater than 30dB.

Abstract: Provided is a distortion-compensated amplifying circuit capable of suppressing distortion without attenuating a level of carrier components, and further obtaining a larger amount of suppression of distortion, which has not been achievable by conventional distortion-compensated amplifying circuit using a pre-distortion technique. A balanced type amplifying circuit is structured such that amplifiers 115 and 116 placed in parallel are sandwiched by 90-degree hybrid circuits 114 and 117. The 90-degree hybrid circuit 114 is supplied with an original signal including carrier components and a distortion signal including distortion equal in amplitude and opposite in phase (having a phase difference of 180 degrees) to distortion that occurs when the original signal is amplified by the amplifiers 115 and 116. The 90-degree hybrid circuit 114 performs a process of differential amplification with a phase difference of 180 degrees between the original signal and the distortion signal.

Abstract: The input signal (110) to a non-linear amplifier (112) is predistorted by injecting a correction signal at coupler (124). To generate the correction signal, a sample of the input signal is amplified using amplifier (130) which has substantially the same distortion generating characteristics as amplifier (112). The output of amplifier (130) is sampled, and the main tone energy is removed at (138), leaving the correction signal for injection to the main signal path. The main portion of the output of amplifier (130) is added coherently to the output of amplifier (112) to enhance efficiency. The correction signal can be manipulated to correct distortion in the output of combiner (152) due to the main portion of the output of amplifier (130).

Abstract: A feedforward amplifier includes a first power splitter for dividing an input signal into two paths. The first path, in sequence, includes a first vector adjuster, a main amplifier, a second power splitter and a delay circuit. The second path, in sequence, includes a delay circuit, a distortion detecting power combiner, a second vector adjuster and an error amplifier. The distortion detecting power combiner combines a portion of a signal from the first path with a signal in the second path. Each vector adjuster adjusts amplitude and phase of a signal in each path. A distortion suppression power combiner synthesizes a signal in the first path with a signal in the second path. Control is included for stopping operation of the error amplifier or main amplifier based on a predetermined condition.

Abstract: A feedforward amplifier which is one of the leading element of linearization systems for mobile communications base stations, and a method of improving the performance thereof, are provided. More particularly, provided are a feedforward amplifier using imperfect cancellation of a main signal and a method of improving the performance thereof, in which by including a predetermined amount of a main signal in an error signal that is input to an error signal cancellation loop of the feedforward amplifier, more error components of a final output signal are removed such that the linearity and efficiency of the final output signal improve.

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: A feed forward amplifier employing high efficiency main and/or error amplifiers with amplifier devices biased in a lower bias class. Small signal nonlinearities in the gain response of the amplifier devices are compensated by a small signal gain adjustment circuit. The resulting gain response is substantially linear over the entire usable range of RF input power.

Abstract: An RF power amplifier linearizer uses a switched distortion power-minimization routine, or simultaneous correlation and power-minimization routines to adjust operational parameters of a vector modulator and a predistortion operator feeding the RF amplifier. The switched power-minimization routine controls the vector modulator, and then adjusts coefficients of the predistorter using the same power minimization routine. The continuous correlation and power minimization routine adjusts the predistortion unit by means of a power minimization unit, and uses a correlator based control mechanism to control the vector modulator simultaneously with the power minimization routine's control of the predistortion unit.

Abstract: A linearized amplification apparatus includes a means for dividing an input signal into a main channel signal and a subsidiary channel signal, a PAR (Peak-to-Average power Ratio) adjustment block for reducing a PAR of the main channel signal to generate a sub-main signal having a reduced PAR compared to the PAR of the main channel signal, an error extraction block for extracting an error signal from the subsidiary channel signal and amplifying the error signal, the amplified error signal corresponding to distortion components in the sub-main signal, and a means for coupling the sub-main signal with the amplified error signal to generate an output signal having an increased PAR compared to the PAR of the sub-main signal.

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 amplifier system (120, 820) for radio frequency signals comprises a phase and gain adjuster (122) which receives an input signal and a control vector (C) for producing a distortion-adjusted input signal. The distortion-adjusted input signal is applied to a main amplifier (126) which generates an amplified output signal. A control loop generates a control vector (P) indicative of distortion of the main amplifier. A modified pre-distortion vector generator (199, 899) generates a modified pre-distortion vector (P′) which is combined with the control vector to produce a composite control vector (Comp). The composite control vector is applied to the phase and gain adjuster, thereby enabling the phase and gain adjuster to produce the distortion-adjusted input signal.

Abstract: An amplifier and bypass switch circuit includes a circuit input, a circuit output, an amplifier and a switching circuit. The amplifier has an amplifier control input, and a first amplifier output. The amplifier control input is connected to the circuit input. The amplifier output is connected to the circuit output. The switching circuit includes a control input, a switch input, a switch output and a phase matching network. The switch output is connected to the circuit output. The switch input is connected to the circuit input. The phase matching network preserves phase information when the amplifier and bypass switch circuit switches between an amplifier mode and a bypass mode.

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: A delay circuit for the secondary path of a feed-forward high power amplifier is disclosed. A first 3 dB quadrature hybrid coupler is coupled to first and second resonator circuits that are resonant at a first resonant frequency. The output of the first hybrid coupler is coupled to the input of a second 3 dB quadrature hybrid coupler. The second hybrid coupler is coupled to third and fourth resonator circuits that are resonant at a second resonant frequency that is greater than the first resonant frequency. The overall combined delay response of the first hybrid coupler and the second hybrid coupler appearing at the fourth node of the second hybrid coupler is substantially constant between the first resonant frequency and the second resonant frequency.

Abstract: An amplifier system (120) for radio frequency signals comprises a combination of a phase and gain adjuster (122) and a first amplifier (123) which receives an input signal and generates a first amplified signal having a gain adjusted in accordance with a gain of the phase and gain adjuster. A main amplifier (126) receives the first amplified signal and generates a second amplified signal. A first controller (134) uses a signal derived from the second amplified signal to generate a first control signal. The first control signal is applied to the phase and gain adjuster to control the gain of the phase and gain adjuster. A second controller (170) is connected to receive the first control signal and to generate a second control signal which is applied to the first amplifier. The second control signal is generated to control the first control signal and thereby control noise of the amplifier system.

Abstract: A feedforward amplifier circuit (30) compensates for distortion introduced into an amplified input carrier signal (34) by amplifying and feedforwarding a distortion signal component from one or more of the amplifiers (32a-32n) in an amplifier array (32) used to amplify the input carrier signal (34). Specifically, a main power amplifier (31) includes a plurality of combined power amplifiers (32a-32n) for amplifying the input carrier signal (34) to create an amplified carrier signal with a carrier signal component and a distortion signal component. The amplified carrier signal (34) is amplified on a main output path.

Abstract: A bandpass amplifier for use in a communication system is described. The amplifier includes a filter, a quantizer, a driver, and a feedback loop. The filter filters the input signal, thereby generating a filtered signal. The quantizer quantizes the filtered signal into one of two values, thereby generating a quantized signal. The driver amplifies the quantized signal, thereby generating the output signal. The feedback loop feeds the output signal to the filter. The quantizer has characteristics in which the quantized signal does not fluctuate between the two values when the input signal is substantially stable.

Abstract: An amplifier architecture using actively phase-matched feed-forward linearization includes: a first signal path having a scaling amplifier 40 in series with a main amplifier 42; a second signal path having a replica amplifier 44 in series with a correction amplifier 46; and a combining node 48 that combines the first signal path and the second signal path. This topology places the scaling amplifier 40 in the main signal path. By inverting the scaling factor from &bgr; to 1/&bgr;, this topology retains the distortion cancellation property while balancing the two signal paths. In this case the scaling amplifier 40 attenuates the input signal rather than amplifying it. The end result remains the same. The main amplifier output signal is lower than the replica amplifier's by a factor of &bgr;. This results in a third-order distortion component that is &bgr;3 times bigger at the replica amplifier output.