Abstract: Protocols and algorithms for contention-based adaptive modulation networks, typically used in unlicensed bands. A wireless system in which high modulation rate packets are prioritized over low rate packets. The wireless system is configured to process communication signals from plural user portable devices having wireless access points capable of dynamically adjusting access point transmit power on a user-by-user basis to a minimum level required to achieve a target signal-to-noise ratio from each user portable device irrespective of the interference observed on the link is also disclosed. The wireless system is also capable of dynamically adjusting access point transmitter power and receiver sensitivity on a user-by-user basis to a minimum level required to achieve the highest possible modulation rate.

Abstract: Disclosed are systems and methods related to reducing intermodulation products in an RF output signal by matching an impedance of the power amplifier to an impedance of the antenna and concurrently blocking signals having a second fundamental frequency received by the antenna when the antenna is transmitting to inhibit intermodulation products of the first and second fundamental frequencies from re-radiating from the antenna. The matching and blocking are performed concurrently by a single circuit with combined matching and blocking functionality.

Abstract: A transmitter comprising a power amplifier, a phase modulator, a switched DC-DC converter, all operating in dual mode, and a controller is disclosed. The power amplifier is arranged to selectively operate either in a first mode or in a second mode, wherein the first mode is a linear mode and the second mode is a non-linear mode in order to save power with least increasing cost in hardware. The transmitter is adapted to operate at different allocated bandwidths, for different radio standards while keeping minimum power consumption governed by the controller. A transceiver, a communication device, a method and a computer program are also disclosed.

Abstract: The present invention addresses method, apparatus and computer program product for controlling a Direct Learning Algorithm. Thereby, a power amplifier operating in a non-linear state is controlled. A signal to be amplified is input to a pre-distorter provided for compensating for non-linearity of the power amplifier. The pre-distorted output signal is forwarded from the pre-distorter to the power amplifier. Parameters of the pre-distorter are adapted in plural steps based on an error between a linearized signal output from the power amplifier and the signal to be amplified using an adaptive direct learning algorithm. It is detected whether the error diverges; and adapting of the parameters of the pre-distorter is stopped when it is determined that the error is diverging.

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

Abstract: A method is provided for simulating intermods of a signal including multiple carriers. The method includes receiving parameters of the signal, the parameters including a total number of carriers, a frequency of one carrier and a spacing between adjacent carriers; identifying multiple intermod combinations corresponding to a desired intermod order; and synthesizing multiple intermod envelopes corresponding to the intermod combinations according to multiple predetermined algorithms using at least one of the total number of carriers, the frequency of the one carrier, and the spacing between adjacent carriers. The predetermined algorithms including at least one predetermined algorithm corresponding to each intermod combination of the multiple intermod combinations.

Abstract: A high-linearity linearizer system includes a multi-stage linearizer circuit formed by cascading multiple linearizer circuits. The multi-stage linearizer circuit is configured to pre-distort an input signal to generate a pre-distorted signal. A non-linear high-power amplifier (HPA) having non-linear characteristics is coupled to the multi-stage linearizer circuit and is configured to amplify the pre-distorted signal. Pre-distortion characteristics of the multi-stage linearizer circuit are configured to counter the non-linear characteristics of the non-linear HPA and to compensate a non-linearity of the non-linear HPA to achieve a desired level of linearity.

Abstract: An electronic device includes an antenna, a wireless transmitter, a proximity sensor and a controller. The antenna includes a first radiating element and a second radiating element which has a different length than the first radiating element. The wireless transmitter is to send a radio signal to the antenna and the controller is to disable the first radiating element in response to the proximity sensor detecting a body part.

Abstract: Certain aspects of the present disclosure provide methods and apparatus for amplifying signals with an amplification circuit. The amplification circuit generally includes a first transistor, an input path coupled between an input node of the amplification circuit and a control input of the first transistor, and a feedforward path coupled between the input node and a feedforward node. In certain aspects, the amplification circuit may also include a first resistive device coupled between the feedforward node and the control input of the first transistor, a biasing circuit coupled to the feedforward node, and a low-impedance path coupled to the feedforward node.

Abstract: A distortion compensation apparatus includes: a filtering unit that is provided with a plurality of storing units each of which is capable of storing a signal therein and that filters an input signal by sequentially moving the input signal starting from a storing unit provided on a first stage up to another storing unit provided on a final stage; a calculating unit that calculates a power level of a signal output from a storing unit that is provided on an earlier stage than the storing unit provided on the final stage; an output unit that, on the basis of the power level calculated, outputs a distortion compensation coefficient used for cancelling out non-linear distortion occurring in an amplifier; and a distortion compensation unit that performs a distortion compensation process on a signal output from the storing unit provided on the final stage, by using the distortion compensation coefficient.

Abstract: A control system and data acquisition system for an electrical capacitance tomography sensor comprised of a sensor having a plurality of electrodes, where each electrode is further comprised of a plurality of capacitance segments. Each of the capacitance segments of each electrode can be individually addressed to focus the electric field intensity or sensitivity to desired regions of the electrodes and the sensor.

Abstract: Reducing non-linear distortions of an electronic device by performing at least the following: receiving, at an output stage circuit of an amplifier, an input signal from a previous stage circuit of the amplifier, driving a first subset of output transistors within the output stage circuit with an auxiliary buffer circuit to generate a first half cycle of an output signal Vout, driving a second subset of output transistors within the output stage circuit with the input signal to generate the first half cycle of the output signal Vout, and driving a set of output transistors with the input signal to generate a second half cycle of the output signal Vout, wherein the auxiliary buffer circuit equalizes the overall current gain associated with the first and second subset of output transistors with the overall current gain associated with the set of output transistors.

Abstract: A method of linearizing a relationship between a signal to an amplifier and an output signal from the amplifier includes applying an inverse of a transfer function of the amplifier to the signal prior to presenting the signal as the amplifier input. The inverse transfer function is represented by a polynomial defined by a set of coefficients. The transmitter output signal is measured by the idle receiver in a time division duplex system. The output signal is filtered to isolate intermodulation products of a selected order and the peak power of the isolated intermodulation products is then estimated. An adaptive algorithm is applied in response to the estimate of the peak power to update the set of coefficients of the polynomial representing the inverse of the transfer function of the amplifier.

Abstract: A radio frequency (RF) amplification method, comprising: modulating a first digital carrier signal with a digital envelop signal to generate digital RF pulse signals having a first frequency, converting the digital RF pulse signals into analog RF pulse signals, amplifying the analog RF pulse signals to generate an RF output signal, converting an analog feedback signal sampled from the RF output signal into digital feedback signals; demodulating the digital feedback signals with a second digital carrier signal to generate an in-phase (I) signal and a quadrature (Q) signal, and generating an amplitude setting signal for adjusting an amplitude of the digital envelop signal and a phase setting signal for adjusting a phase of the first digital carrier signal according to the I signal and the Q signal.

Abstract: An RF hybrid coupler with phase and attenuation control that efficiently combines the functions of phase shifting and attenuation within a circuit. Embodiments include a hybrid coupler connected to parallel resistance-reactance (RX) circuits, where the reactance X may be a capacitor C or an inductor L; a hybrid coupler connected to parallel RX circuits (which may be variable), each of which is in turn series coupled to an inductive element L which corrects for attenuation range collapse while providing for fairly flat phase shift and attenuation performance as a function of frequency; and two hybrid couplers in a combined phase shifter and attenuator configuration, each with opposite frequency-dependent slopes and cascaded in series such that the slopes substantially cancel each other out, resulting in flat responses versus frequency.

Abstract: A linearization circuit reduces intermodulation distortion in an amplifier that includes a first stage and a second stage. The linearization circuit receives a first signal that includes a first frequency and a second frequency and generates a difference signal having a frequency approximately equal to the difference of the first frequency and the second frequency, generates an envelope signal based at least in part on a power level of the first signal, and adjusts a magnitude of the difference signal based on the envelope signal. When the amplifier receives the first signal at an input terminal, the first stage receives the adjusted signal, and the second stage does not receive the adjusted signal, intermodulation between the adjusted signal and the first signal cancels at least a portion of the intermodulation between the first frequency and the second frequency from the output of the amplifier.

Abstract: Disclosed is a method of operating an electronic device to transmit an RF signal. The method includes: selecting output power of a PA included in the electronic device, which is required when a signal is transmitted through an antenna included in the electronic device; determining input power of the PA corresponding to the output power of the PA by using at least one of a first data point, a second data point, or a plurality of data points stored in a memory included in the electronic device; and controlling output power of an RF transmission circuit included in the electronic device based on the input power, wherein the plurality of data points are generated by being linearly interpolated between the first data point and the second data point. Various embodiments are possible.

Abstract: The present invention addresses method, apparatus and computer program product for stabilization of the direct learning algorithm for wideband signals. Thereby, a signal to be amplified is input to a pre-distorter provided for compensating for non-linearity of the power amplifier, and the pre-distorted output signal from the pre-distorter is forwarded to the power amplifier. Parameters of the pre-distorter are adapted based on an error between the linearized signal output from the power amplifier and the signal to be amplified using an adaptive direct learning algorithm, and the linear system of equations formed by the direct learning algorithm are solved using a conjugate gradient algorithm, wherein, once per direct learning algorithm adaptation, at least one of the initial residual and the initial direction of the conjugate gradient algorithm are set based on the result of the previous adaptation.

Abstract: A system and method compensates distortions in transmission line measurement by obtaining a frequency response of a transmission line responsive to a test signal; approximating the frequency response as a function of a complex valued variable; and applying an analytic continuation to extend the function of the complex valued variable to a modified frequency response corresponding to a lossless frequency response, to compensate for loss in the transmission line. The modified frequency response may be further sampled at linearly spaced points in a wave number domain to compensate for dispersion of the transmission line.

Abstract: The present application provides a multimode transmit power control loop, an electronic device, and a method of adjusting a detected operating level of amplified power output from a power amplifier. The multimode transmit power control loop including a feedback path wherein a feedback path signal is coupled to a feedback detection input of the power amplifier via the feedback path. The feedback path includes a mode selection switch having a control input for selectively applying a different impedance circuit to the feedback path for switching in different attenuation levels, based upon the control input of the mode selection switch identifying one or more of multiple potential operating modes. Operation of the multimode transmit power control loop increases or decreases an operating level of amplified power output from the power amplifier, which is proportional to a present level of attenuation resulting from the particular impedance circuit being applied to the feedback path via the mode selection switch.

Abstract: A power amplifier according to examples includes an amplifying circuit configured to amplify an input signal, a feedback circuit configured to feedback the amplified signal to the amplifying unit, and a feedback controlling circuit configured to control a power of the fed-back signal based on a power of the input signal. The feedback controlling unit performs controlling so that the power of the fed-back signal is increased as the power of the input signal is increased.

Abstract: A phased array transmitter includes a plurality of vector modulators, an in-phase/quadrature (I/Q) signal generator, and a multiphase generator. The output phases of the plurality of vector modulators, and hence the direction of transmission of the phased array transmitter, are set and controlled by adjusting both the magnitude ratios of I/Q signal pairs generated by the I/Q signal generator and applied to I and Q inputs of the plurality of vector modulators and phases of a plurality of local oscillator (LO) signal phases generated by the multiphase generator and applied to LO inputs of the plurality of vector modulators.

Abstract: A linearized MIMO system which includes a MIMO receiver which comprises one or more receiving units, each receiving unit comprises one or more receiving antennas and an optional MIMO spatial decoder. The linearized MIMO system also includes a linearized MIMO transmitter, which comprises a plurality of non-linear power amplifiers at respective transmission branches, where each of the non-linear power amplifiers feeds a respective antenna with an amplified signal. The linearized MIMO system also includes a MIMO spatial pre-coder for receiving an artificial data signal from a global linearizer, and based on a channel state information of the medium (medium-channel), the linearized MIMO system creates a plurality of transmission branch-signals. Each of the branch signals feeds one of the non-linear power amplifiers, respectively. The global linearizer receives a data signal and creates the artificial data signal.

Abstract: A self-oscillating amplifier system is disclosed. The system comprises a pulse modulator, a switching power amplification stage and a demodulation filter. Moreover, the system comprises a compensator including a forward filter which is a high order filter including a second order pole pair and a second order zero pair. Hereby it is possible to decrease the phase turn at low frequencies for better stability and increasing the gain of the control loop within the desired bandwidth.

Abstract: A multi-mode envelope tracking (ET) amplifier circuit is provided. The multi-mode ET amplifier circuit can operate in a low-resource block (RB) mode, a mid-RB mode, and a high-RB mode. The multi-mode ET amplifier circuit includes fast switcher circuitry having a first switcher path and a second switcher path and configured to generate an alternating current (AC) current. A control circuit activates the fast switcher circuitry in the mid-RB mode and the high-RB mode, while deactivating the fast switcher circuitry in the low-RB mode. More specifically, the control circuit selectively activates one of the first switcher path and the second switcher path in the mid-RB mode and activates both the first switcher path and the second switcher path in the high-RB mode. As a result, it is possible to improve efficiency of ET tracker circuitry and the multi-mode ET amplifier circuit in all operation modes.

Abstract: Systems and methods are provided for aligning amplitude and phase signals in a polar receiver. A receiver generates digital amplitude and phase signals representing the amplitude and phase of a modulated input signal. At least one of the digital signals is filtered using a fractional delay filter with a variable delay. The delay of the fractional delay filter is adjusted to align the amplitude and phase signals. In some embodiments, an error vector magnitude is determined by comparing in-phase and quadrature values of the signal with values corresponding to a constellation point, and the delay is adjusted based on the error vector magnitude. The fractional delay filter may be a finite impulse response filter with coefficients stored in a lookup table that correspond to different delays.

Abstract: An apparatus and a method for controlling power consumption of a terminal in a wireless communication system are provided. The method includes deactivating one or more of hardware components for signal reception in a transmission interval if there is no data to be received in the transmission interval, and receiving a control signal by activating all the components in a next transmission interval.

Abstract: Disclosed are devices and methods for improving power added efficiency and linearity of radio-frequency power amplifiers implemented in flip-chip configurations. In some embodiments, a harmonic termination circuit can be provided so as to be separate from an output matching network configured to provide impedance matching at a fundamental frequency. The harmonic termination circuit can be configured to terminate at a phase corresponding to a harmonic frequency of the power amplifier output. Such a configuration of separate fundamental matching network and harmonic termination circuit allows each to be tuned separately to thereby improve performance parameters such as power added efficiency and linearity.

Abstract: A circuit includes a first amplifier path comprising a first amplifier, MA, a second amplifier path comprising a cascode device and a second amplifier, MB, a node defined by a source of the cascode device and a drain of the second amplifier, MB, and a capacitance coupled between the node and a source of the second amplifier, MB.

Abstract: A distortion compensation apparatus include: a feedback unit that generates a feedback signal containing a first frequency component in which a plurality of odd-order distortions are superimposed and a second frequency component in which a plurality of even-order distortions are superimposed according to output of a power amplifier which amplifies a transmission signal; and a signal processor that separates the first frequency component and the second frequency component from the generated feedback signal and performs signal processing.

Abstract: A radio frequency (RF) front end chip in a phased array antenna panel for transmitting a modulated circularly-polarized signal is disclosed. The RF front end chip includes an oscillator providing an angular speed modulation signal to a quadrature generation block, the quadrature generation block providing an in-phase signal and a quadrature signal based on the angular speed modulation signal, a first amplifier receiving the in-phase signal and a data signal, and providing a modulated horizontally-polarized signal, and a second amplifier receiving the quadrature signal and the data signal, and providing a modulated vertically-polarized signal, where a modulated circularly-polarized signal is generated based on the modulated horizontally-polarized signal and the modulated vertically-polarized signal. The angular speed modulation signal controls an angular speed of the modulated circularly-polarized signal. The data signal is encoded by the angular speed modulation signal.

Abstract: A high-frequency power amplifying module is provided for a communication device that simultaneously uses at least a radio wave in a first band and a radio wave in a second band, and a first high-frequency power amplifier for the first band and a second high-frequency power amplifier for the second band are mounted. The first band and the second band are frequency bands that produce intermodulation distortion of a frequency included in the receive frequency band of the second band, due to a transmit frequency of the first band received by the first high-frequency power amplifier and a transmit frequency of the second band received h the second high-frequency power amplifier. The second high-frequency power amplifier includes a filter that blocks a signal at the transmit frequency of the first band.

Abstract: Aspects of a method and system for high-speed, low-power optical communications are provided. In one embodiment, a system for optical communications comprises a digital-to-analog converter (DAC), a driver, and a transmit optical subsystem. The DAC is operable to receive a digital code of a plurality of digital codes and output an analog current signal having an analog current level of a plurality of analog current levels. The driver is operable to condition the analog current signal output from the digital-to-analog converter. The transmit optical subsystem is operable to generate an optical power signal from the conditioned analog current signal. A mapping between the plurality of digital codes and the plurality of analog current levels is dynamically controlled according to one or more characteristics of the optical power signal. The one or more characteristics comprise or a symbol amplitude sensitivity and/or a nonlinearity that may be temperature dependent.

Abstract: An ultrasound imaging system includes a plurality of processing chains (2061, . . . , 206K) for a plurality of transducer element channels (1081, . . . , 108K). A processing chain of the plurality of processing chains, includes: a phase rotation processor (1141, . . . , 114K) that focuses an N-bit digital representation, of an analog RF signal received on the corresponding transducer element channel, through phase rotation through phase additions or subtractions, and outputs a focused N-bit quantized value, where N is a predetermined positive integer.

Abstract: An embodiment of the invention is a time-delay invariant predistortion approach to linearize power amplifiers in wireless RF transmitters. The predistortion architecture is based on the stored-compensation or memory-compensation principle by using a combined time-delay addressing method, and therefore, the architecture has an intrinsic, self-calibrating time-delay compensation function. The predistortion architecture only uses a lookup table to conduct both the correction of non-linear responses of a power amplifier and the compensation of any time-delay effects presented in the same system. Due to the time-delay invariant characteristic, the predistortion design has a wider dynamic range processing advantage for wireless RF signals, and therefore can be implemented in multi-carrier and multi-channel wireless systems.

Abstract: An apparatus to apply frequency selective digital predistortion (DPD) to a power amplifier (PA) circuit is disclosed. The apparatus comprises a first transformation circuit configured to receive a PA input comprising a quantity indicative of an input signal of the PA circuit and process the PA input by applying a first predetermined weighted function, to form a processed PA input, and a second transformation circuit configured to receive a PA output comprising a quantity indicative of an output signal of the PA circuit and process the PA output by applying a second predetermined weighted function, to form a processed PA output. The apparatus further comprises a coefficient computation circuit configured to receive the processed PA input and the processed PA output; and estimate distortion coefficients, to be utilized for predistorting the input signal of the PA circuit, based on the processed PA input and the processed PA output.

Abstract: An adaptive linearizer system includes an adaptive linearizer circuit that is configured to pre-distort an input signal based on one or more control signals to generate a pre-distorted signal, and a non-linear high-power amplifier (HPA) having non-linear characteristics that is coupled to the adaptive linearizer circuit. The nonlinear HPA amplifies the pre-distorted signal. The pre-distortion characteristics of the adaptive linearizer circuit provide for countering the non-linear characteristics of the non-linear HPA and compensating a non-linearity of the non-linear HPA.

Abstract: A technique for determining a time alignment (TA) error in a circuitry is provided. One or few measurement cycles can be utilized for a closed-loop TA alignment, e.g., for envelope tracking in a transmitter. As to a method aspect of the technique, the amplitudes of a first signal and a second signal are determined. A first measure is computed that is indicative of a relative amplitude error, and a second measure is computed that is indicative of a variation of at least one of the amplitudes. The TA error is determined by correlating the first and second measures.

Abstract: A power amplifier gain attenuation circuit includes: a gain attenuation (reduction) circuit configured to receive an input signal, an external drive signal and a bias voltage, and output a secondary input signal after attenuating the input signal depending on the drive signal and bias voltage; an amplifier including: a bias input terminal configured to receive a bias voltage; a signal input terminal configured to receive a secondary input signal, and an output terminal configured to output a gained output signal. The power amplifier gain attenuation circuit can reduce a gain effectively, and the amount of phase jump caused by the attenuation is quite small.

Abstract: An apparatus and a method for controlling power consumption of a terminal in a wireless communication system are provided. The method includes deactivating one or more of hardware components for signal reception in a transmission interval if there is no data to be received in the transmission interval, and receiving a control signal by activating all the components in a next transmission interval.

Abstract: Digital pre-distortion is performed on a received signal using a set of pre-distortion coefficients to produce a digital pre-distorted signal. The digital pre-distorted signal is converted to an analog signal, which is amplified to produce a transmission output signal. The transmission output signal is converted to a digital feedback signal. A plurality of fractional delay filters is applied to the digital feedback signal to obtain a plurality of fractional delay compensated (FDC) candidates, and gain compensation is applied to each of the plurality of FDC candidates to obtain a plurality of gain and fractional delay compensated (XFT) candidates. The digital pre-distorted signal is used as a reference signal, and the XFT candidates and the reference signal are used to select a selected XFT candidate of the plurality of XFT candidates. The selected XFT candidate is used to generate the set of pre-distortion coefficients.

Abstract: Various examples are directed to systems and methods for digital predistortion (DPD). A linear digital predistortion (DPD) circuit may be programmed to generate a pre-distorted signal linear component based at least in part on a complex baseband signal. A nonlinear DPD circuit may be programmed to generate a pre-distorted signal nonlinear component based at least in part on the complex baseband signal. A mixer circuit programmed to generate a pre-distorted signal based at least in part on the pre-distorted signal linear component and the pre-distorted signal nonlinear component.

Abstract: A high throughput satellite communication system and method of satellite communication that provide loopback capability and increased throughput is disclosed. The satellite communication system and method of satellite communication utilize pre-distortion based on remotely estimated characteristics of a satellite transponder's power amplifier (PA). The pre-distortion is applied to the hub modulator's constellation.

Abstract: A delay estimation method for a multiple input multiple output communications system, includes: calculating, by a receiver, a channel response matrix of a Multiple input multiple output MIMO communications system, where there are n transmit channels and m receive channels in the MIMO communications system, n?2, m?2, and the channel response matrix includes channel responses of n*m sub-channels; calculating, by the receiver, an integer delay, relative to a reference sub-channel, of each of the n*m sub-channels according to the channel response matrix, where the reference sub-channel is any sub-channel in the n*m sub-channels; calculating, by the receiver, fraction delays of the n*m sub-channels according to the channel response matrix; and separating out, by the receiver, delays of the m receive channels according to delays of the n*m sub-channels.

Abstract: Provided is a receiver including an oscillator (OSC) configured to generate an oscillation signal based on a radio signal, a clocked envelope detector (ED) configured to detect an envelope of the oscillation signal and hold a peak value of the envelope during a time interval, and an analog-to-digital converter (ADC) configured to convert the peak value of the envelope into a digital signal.

Abstract: A low noise amplifier (LNA) reduces matching and switch noise. The LNA includes a main radio frequency signal path, an auxiliary radio frequency signal path and a phase shifter. The main path includes a first transistor and an inductor. The inductor is positioned between an input port of the LNA and the first transistor. The first transistor receives an input radio frequency signal via the inductor and provides a first amplified signal based on the input radio frequency signal. The auxiliary radio frequency signal path provides a second amplified signal for a noise cancellation mode based on the input radio frequency signal. The phase shifter applies a phase shift to an output signal of the LNA based on the first amplified signal and the second amplified signal.

Abstract: A method and apparatus for intermodulation product (IMP) cancellation. In one embodiment, the method comprises: acquiring copies of source signals that create IMPs in a passband of interest; creating copies of the IMPs for use as IMP cancellation signals by either multiplying the source signals together as a series of digital samples such that the multiplied signals create a near real and continuous time copy of the IMPs or creating a sum of the source signals in near real and continuous time and convolving the sum of the source signals with a mathematical model to effectively multiply the signals together to create a copy of the IMPs; adjusting one or both of phase and amplitude of the copies; and using the copies to cancel the IMPs inband of the passband of interest.

Abstract: A controller can include a signal generator configured to provide an input signal to a modulator. The controller can be configured to generate a modulator compensation parameter in response to a modulated feedback signal corresponding to an output of the modulator. The controller can also be configured to generate a power amplifier predistortion signal in response to an amplified feedback signal corresponding to an output of a power amplifier coupled to the modulator.

Abstract: A predistortion system for correcting a distortion of a distorting component is provided. It comprises a signal generator, adapted to generate a first signal based upon a reference signal, the distorting component, adapted to generate a second signal, based upon the first signal, and an iterative predistortion device, adapted to determine a compensated signal based upon the second signal and the reference signal. The signal generator is adapted to use the compensated signal as reference signal in further iterations after a first iteration. The predistortion system moreover comprises a predistortion calculation device, adapted to determine a predistortion function based upon the reference signal and the first signal. The signal generator is then adapted to generate the first signal based upon the predistortion function for further reference signals.

Abstract: An apparatus for controlling the gain and phase of an input signal input to a power amplifier comprises a gain control loop configured to control the gain of the input signal based on power levels of the input signal and an amplified signal output by the power amplifier, to obtain a predetermined gain of the amplified signal, and a phase control loop configured to obtain an error signal related to a phase difference between a first signal derived from the input and a second signal derived from the amplified signal, and control the phase based on the error signal, to obtain a predetermined phase of the amplified signal. The phase control loop delays the first signal such that the delayed first signal and the second signal used to obtain the error signal correspond to the same part of the input signal. The apparatus may be included in a satellite.