Disclosed is an envelope tracking (ET) system having a transmit (TX) section, a power amplifier (PA), a fast switched-mode power supply (Fast SMPS), and control circuitry. The TX section receives an input signal and provides a modulated signal to the PA. The TX section also generates an ET signal based on a modulation envelope of the modulated signal. The TX section provides an envelope control (EC) signal based on the ET signal to modulate a supply signal provided to the PA by the Fast SMPS. The control circuitry provides a transmit TX gain signal and an ET gain signal to the TX section based on a PA temperature signal, a TX temperature signal, a target power signal, a measured power signal. The control circuitry is configured to maintain the efficiency and linearity of the PA over a wide operating temperature range.

A method includes determining one or more characteristics of a system that uses a power amplifier. The method also includes determining, based on the one or more determined characteristics, a switching speed and a supply voltage for the power amplifier. The method further includes modulating a power supply of the power amplifier according to the determined switching speed and supply voltage.

An electronic device is provided. The electronic device may include a plurality of antennas configured to transmit and receive a signal in a radio frequency (RF) frequency band; and an RF circuit configured to process the signal in the RF frequency band. The RF circuit includes a reception (Rx) path configured to transfer a first signal received through the plurality of antennas, a transmission (Tx) path configured to transfer a second signal to the plurality of antennas, and a coupler configured to transfer at least a part of the second signal obtained in the Tx path to the Rx path. The Tx path includes a power divider configured to distribute power to at least one antenna among the plurality of antennas, and the coupler is electrically connected to an input terminal of the power divider to be disposed before the power divider.

The invention discloses a transmitter comprising a pulse encoder for creating pulses from the amplitude of an input signal to the transmitter, a compensation signal generator for cancelling quantization noise caused by the pulse encoder, a mixer or I/Q modulator for mixing an output of the pulse encoder with the phase of an input signal to the transmitter, said output of the pulse encoder comprising the amplitude of the complex input signal plus the quantization noise caused by the pulse encoder, and an amplifier for creating an output signal from the transmitter. In the transmitter, a control signal (C.sub.A) for controlling a function of the amplifier comprises an output signal from the compensation signal generator, and an input signal to the amplifier comprises an output from the mixer having been modulated to a desired frequency.

A method includes receiving a signal from a remote transmitter via an electrically-tunable antenna having a tunable element. An adjustment, to be applied to a response of the electrically-tunable antenna, is calculating by analyzing the received signal. The response of the electrically-tunable antenna is adapted by controlling the tunable element responsively to the estimated adjustment.

A digital frontend circuit for a radio frequency (RF) comprises a digital predistortion (DPD) block, a plurality of sub-sample delay elements, and a selection circuit. The DPD block for computing predistorted transmit signals according to a Volterra series approximation model. The DPD block has an input for receiving input samples at a first sample rate and an output for providing the predistorted transmit signals at the first sample rate. Each of the sub-sample delay elements provides a delay to an input sample as specified by the Volterra series approximation model, where each of the delays is based on a fraction of the first sample rate. The selection circuit selects one of the plurality of sub-sample delay elements in response to a selection signal from the digital predistortion block. The selection signal for selecting a delay as specified by the Volterra series approximation model.

A method of characterizing an envelope tracking amplification stage, the method comprising: generating an input test waveform which is representative of an input waveform under normal operating conditions of the amplification stage; applying a respective one of a plurality of different shaping functions, each comprising a non-linear transfer function, to the input signal envelope in each of a plurality of test periods during the period in which the input test waveform is applied as the input signal to generate the input to the envelope tracking modulated supply voltage; measuring parameters of the amplification stage during the period in which the input test waveform is applied in order to allow determination of the gain, phase and efficiency characteristics of the amplifier; and for each of the gain, phase and efficiency characteristics, generating a three dimensional plot of the characteristic with respect to input power and supply voltage applied to the amplifier.

A wireless communication device includes an antenna, a DPDC, an amplifier, a coupler, and a bias output unit. The DPDC performs distortion compensation on a transmission signal based on a feedback signal. The amplifier amplifies the transmission signal subjected to the distortion compensation by the DPDC. The coupler splits the transmission signal amplified by the amplifier into a transmission signal output to the antenna and the feedback signal input to the DPDC. The DPDC measures an index based on a reflected wave obtained by reflection of the transmission signal split by the coupler from the antenna. The bias output unit applies a bias voltage for controlling an efficiency of an amplifier to the amplifier in accordance with the index measured by the DPDC.

The present disclosure relates to a digital frontend system for a radio device comprising a digital filter arranged for receiving digital quadrature signals and for filtering the digital quadrature signals and for outputting filtered quadrature signals; a conversion circuit arranged for receiving the filtered quadrature signals and for performing a rectangular to polar conversion of the filtered quadrature signals and for outputting a plurality of polar signals, characterized in that, the plurality of polar signals comprising an amplitude signal and quadrature phase signals.

A distortion compensation apparatus includes a retention unit that retains a coefficient for distortion compensation for each of a plurality of time segments of a burst signal that keeps a constant power level, and a distortion compensation unit that, by using a coefficient for a time segment that corresponds to elapsed time from a head of the burst signal among the coefficients retained by the retention unit, executes distortion compensation for the time segment.