A RF-digital hybrid mode power amplifier system for achieving high efficiency and high linearity in wideband communication systems is disclosed. The present invention is based on the method of adaptive digital predistortion to linearize a power amplifier in the RF domain. The present disclosure enables a power amplifier system to be field reconfigurable and support multi-modulation schemes (modulation agnostic), multi-carriers and multi-channels. As a result, the digital hybrid mode power amplifier system is particularly suitable for wireless transmission systems, such as base-stations, repeaters, and indoor signal coverage systems, where baseband I-Q signal information is not readily available.

A power amplifier circuit includes a power amplifier that amplifies an input signal and outputs the amplified signal from an output terminal thereof, a first filter circuit that has a frequency characteristic that attenuates an Nth-order harmonic of the amplified signal, N that is an integer greater than or equal to 2, and a second filter circuit that has a frequency characteristic that attenuates the Nth-order harmonic of the amplified signal. The first filter circuit includes a first capacitor and a first inductor. The first capacitor and the first inductor are connected in series between the output terminal and ground. The second filter circuit includes a second capacitor and a second inductor. The second capacitor and the second inductor are connected in series between the output terminal and ground.

A communication method and system for converging a 5th-Generation (5G) communication system for supporting higher data rates beyond a 4th-Generation (4G) system with a technology for Internet of Things (IoT) are provided. The disclosure may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. An amplifier includes a first transistor for amplifying the fundamental signal applied to a gate terminal. and a second transistor having a source terminal electrically connected to the drain terminal of the first transistor and a drain terminal electrically connected to a bias voltage. The current flowing through the second transistor may be determined based on the current flowing in the drain terminal of the first transistor.

An audio amplifier includes an output stage including a first toroidal transformer with a first pair of secondary windings that are coupled in parallel across an output terminal. The output stage further includes a second toroidal transformer with a second pair of secondary windings that are connected in a series combination that is coupled across the output terminal.

Linearizing Power Amplifiers' Outputs in Multi-Antenna System There is provided power efficient and simple structure for linearizing power amplifiers' outputs in multi-antenna beamforming systems. Beamforming factors are obtained for controlling transmission beams of the antennas in an analogue/hybrid beamforming system. At least one power amplifier model is determined on the basis of the power amplifiers' outputs and the beamforming factors. Predistortion parameters, for feeding a predistorted signal to power amplifiers for linearizing the power amplifiers' outputs, are determined such that after the operating parameters of the power amplifiers have been adjusted, errors in power amplifiers' outputs are reduced.

Apparatus and method for extended operational bandwidth amplifiers with fractional instantaneous bandwidth feed forward correction. In one embodiment, the method includes amplifying a radio frequency (RF) input signal to provide an amplified RF signal and introducing a first delay in the amplified RF signal. The method also includes receiving an error signal of the amplified RF signal and centering a correction bandwidth with respect to the amplified RF signal. The method also includes amplifying the error signal and combining the amplified RF signal and the amplified error signal to reduce an error in the amplified RF signal. The first delay is smaller than a second delay caused by the error path.

Various examples are directed to a power amplifier circuit, comprising a digital predistortion circuit, first and second power amplifiers, and a bias feedback circuit. The digital predistortion circuit may be configured to generate a predistorted input signal based at least in part on an input signal. The first power amplifier may be configured to generate a first amplified signal based at least in part on the predistorted input signal. The second power amplifier may be configured to generate a second amplified signal based at least in part on the predistorted input signal. The bias feedback circuit may be configured to adjust at least one of a bias of the first power amplifier or a bias of the second power amplifier to align a first nonlinear behavior of the first power amplifier with a second nonlinear behavior of the second power amplifier.

A method comprises obtaining a transmission signal to be power-amplified in a power amplifier (361) prior to transmission; separating the transmission signal into two or more polyphase components of the transmission signal; feeding one or more polyphase components of the transmission signal comprised in the two or more polyphase components to each of two or more parallel predistortion circuits (320,321,322); selecting a dedicated predistortion model and dedicated predistortion coefficients for each of the two or more parallel predistortion circuits (320,321,322); performing non-linear memory-based modeling on the transmission signal according to the selected dedicated predistortion models and coefficients using the one or more polyphase components; and combining output signals of the two or more parallel predistortion circuits (320,321,322) to form a predistorted transmission signal (y[n]) to be applied to the power amplifier (361).

An envelope tracking (ET) system is provided. The ET amplifies a radio frequency (RF) signal correspond to an amplitude bandwidth exceeding a voltage modulation bandwidth limitation of the ET system. The ET system compresses the amplitude bandwidth to match the voltage modulation bandwidth of the ET system. More specifically, the ET system compresses a predefined voltage waveform, which tracks time-variant amplitudes of a digital form of the RF signal, to generate a modified voltage waveform at a reduced bandwidth. To ensure that signal distortion(s) resulted from the bandwidth compression can be corrected, the ET system nonlinearly modifies predefined amplitude(s) of the predefined voltage waveform to generate modified amplitude(s) of the modified voltage waveform that is never less than the predefined amplitude(s) of the predefined voltage waveform. As such, the ET system can amplify the RF signal with improved linearity and efficiency, without degrading spectral performance of the RF signal.

A technique is presented for correcting phase distortion in a digital wireless transmitter. The technique includes: receiving an RF signal in an analog domain by a digital-to-RF modulator; amplitude modulating, the RF signal in accordance with a digital input code; and introducing delay in a signal path traversed by the RF signal before the digital-to-RF modulator using a delay circuit. The duration of the delay depends upon the value of the digital input code and substantially cancels out the phase distortion introduced by the digital wireless transmitter.