A communication device includes a power amplifier that generates power signals according to one or more operating bands of communication data, with the amplitude being driven and generated in output stages of the power amplifier. The final stage can include an output passive network that suppresses suppress an amplitude modulation-to-phase modulation (AM-PM) distortion. During a back-off power mode a bias of a capacitive unit of the output power network component can be adjusted to minimize an overall capacitance variation. A output passive network can further generate a flat-phase response between dual resonances of operation.

Certain aspects of the present disclosure are directed to digital predistortion (DPD) for use with a multi-chain wireless transmitter. In various examples described herein, the multi-chain transmitter is configured to use a single common DPD device or module for all transmit chains and to adjust the bias voltages of the power amplifiers of the separate transmit chains to operate at substantially the same backoff so the distortion to the corresponding output signals is similar. Since the distortion of the output of the different chains is similar, a single common predistortion may be applied using the single DPD device to a signal to be transmitted. Techniques are also described for calibrating the predistortion coefficients of the DPD to optimize (or otherwise set) the amount of distortion reduction to be achieved. The predistortion coefficients for the single DPD may be set or calibrated based on a particular directionality needed for beamforming.

Systems and methods for radio frequency digital predistortion in a multi-band transmitter are disclosed. In one embodiment, the multi-band transmitter includes a digital upconversion system configured to digitally upconvert digital input signals to provide digital radio frequency signals. Each digital input signal and thus each digital radio frequency signal corresponds to a different band of a multi-band transmit signal to be transmitted by the multi-band transmitter. The multi-band transmitter also includes a radio frequency digital predistortion system configured to digitally predistort the digital radio frequency signals to provide predistorted digital radio frequency signals, and a combiner configured to combine the predistorted digital radio frequency signals to provide a multi-band predistorted digital radio frequency signal.

A communication device includes a power amplifier that generates power signals according to one or more operating bands of communication data, with the amplitude being driven and generated in output stages of the power amplifier. The final stage can include an output passive network that suppresses suppress an amplitude modulation-to-phase modulation (AM-PM) distortion. During a back-off power mode a bias of a capacitive unit of the output power network component can be adjusted to minimize an overall capacitance variation. A output passive network can further generate a flat-phase response between dual resonances of operation.

A communication device includes a power amplifier that generates power signals according to one or more operating bands of communication data, with the amplitude being driven and generated in output stages of the power amplifier. The final stage can include an output passive network that suppresses an amplitude modulation-to-phase modulation (AM-PM) distortion. During a back-off power mode a bias of a capacitive unit of the output power network component can be adjusted to minimize an overall capacitance variation. The output passive network can further generate a flat-phase response between dual resonances of operation.

A radio frequency (RF) amplification system or transmitter includes one or more power amplifiers and a controller that is configured to adjust amplitudes and phases of RF input signals of the one or more power amplifiers and supply voltages applied to the one or more power amplifiers. The system may include a single digital-to-RF modulator and a power divider to drive multiple power amplifiers. A power combiner may also be provided to combine outputs of the power amplifiers. In at least one implementation, amplitude adjustment of the RF input signals of the one or more power amplifiers may be used to provide transmit power control and/or power backoff.

A distortion-compensating power amplifier compensates for nonlinear distortion in a power amplifier. The distortion-compensating power amplifier includes: a predistorter that performs pre-distortion processing, the pre-distortion processing applying an inverse characteristic of a distortion characteristic that is generated in the power amplifier to an input signal; a filter that performs band limitation on the pre-distorted input signal by using a frequency characteristic that is asymmetric with respect to a center frequency of the input signal, the filter having a filter coefficient that is a complex number; a down-sampler that down-samples the band-limited input signal; and a digital-to-analog converter that converts the down-sampled input signal from a digital signal to an analog signal.

A single or multistage signal predistorter includes an input coupled to receive an information signal comprising input samples and an output coupled to the high power amplifier, the signal predistorter configured to receive an input sample, generate a distortion sample based on an estimate of nonlinearity of the high power amplifier at an operating saturation level, modify the input sample with a correction term to generate a predistortion signal, wherein the correction term is proportional to the distortion sample, and further wherein the predistortion signal comprises the information signal modified to account for nonlinearities in the high power amplifier.

A radio frequency (RF) amplification system or transmitter includes one or more power amplifiers and a controller that is configured to adjust amplitudes and phases of RF input signals of the one or more power amplifiers and supply voltages applied to the one or more power amplifiers. The system may include a single digital-to-RF modulator and a power divider to drive multiple power amplifiers. A power combiner may also be provided to combine outputs of the power amplifiers. In at least one implementation, amplitude adjustment of the RF input signals of the one or more power amplifiers may be used to provide transmit power control and/or power backoff.

A single or multistage signal predistorter includes an input coupled to receive an information signal comprising input samples and an output coupled to the high power amplifier, the signal predistorter configured to receive an input sample, generate a distortion sample based on an estimate of nonlinearity of the high power amplifier at an operating saturation level, modify the input sample with a correction term to generate a predistortion signal, wherein the correction term is proportional to the distortion sample, and further wherein the predistortion signal comprises the information signal modified to account for nonlinearities in the high power amplifier.