Nanosemi, Inc.

Massachusetts Institute of Technology

Nanosemi Technologies

Alexandre Megretski

Helen Haeran Kim

Yan Li

Zohaib Mahmood

Kevin Chuang

Yanyu Huang

Vladimir Marko Stojanovic

Yu-Chen Wu

Zhipeng Li

Yehuda Avniel

Omer Tanovic

George Stone, Iv

Dmitri Fomin

Andrew Feldman

Alexandre Marques

Chuang Kevin

Li Yan

Disclosed are systems, methods, and other implementations that include a machine-implemented artificial neural network including a plurality of nodes, with the nodes forming at plurality of layers including an input layer, at least one hidden layer, and an output layer, and a plurality of links, with each link coupling a corresponding source node and a receiving node. At least one link is configured to evaluate a piecewise linear function of a value provided by a first source node, from the plurality of nodes, to yield a value for a first receiving node coupled to the at least one link. Each node of a hidden layer is configured to aggregate values provided by links for which that node is the receiving node of the link, with the first receiving node providing non-linear output resulting, in part, from the at least one link configured to evaluate the piecewise linear function.

Artificial neural network implementations

Disclosed are systems, devices, modules, methods, and other implementations, including a method for digital predistortion that includes receiving, by a digital predistorter, a first signal that depends on amplitude variations based on an input signal, u, with the variations of the first signal corresponding to time variations in non-linear characteristics of a transmit chain that includes a power amplifier. The method further includes receiving, by the digital predistorter, the input signal u, generating, by the digital predistorter, based at least in part on signals comprising the input signal u and the first signal, a digitally predistorted signal v to mitigate the non-linear behavior of the transmit chain, and providing the predistorted signal v to the transmit chain.

Linearization with level tracking

A received signal is enhanced by removing distortion components of a concurrently transmitted signal. A received signal is acquired in a receive frequency band concurrently with transmission of a transmit signal in a transmit frequency band. The received signal includes an intermodulation distortion component of the transmit signal. A representation of the transmit signal is processed using a non-linear predictor to output a distortion signal representing predicted distortion components in the received signal. The received signal is enhanced using the distortion signal by removing the predicted distortion components from the received signal corresponding to the distortion signal.

Passive intermodulation cancellation

Disclosed are methods, systems, devices, apparatus, media, design structures, and other implementations, including a method is that includes receiving, at a receiver device, a signal transmitted from a remote wireless device, with the signal including a training sequence, and updating, based on the training sequence, one or more adjustable characteristics for a non-linear equalizer of the receiver device, with the one or more adjustable characteristics controlling signal non-linear compensation processing to correct non-linear distortions affecting communication signals transmitted from the remote wireless device. In some embodiments, the method may further include updating, based on the training sequence, additional one or more adjustable characteristics for a linear equalizer of the receiver device, with the additional one or more adjustable characteristics controlling signal linear compensation processing to correct linear distortions affecting the communication signals.

Non-linear equalizer in communication receiver devices

A pre-distorter that both accurately compensates for the non-linearities of a radio frequency transmit chain, and that imposes as few computation requirements in terms of arithmetic operations, uses a diverse set of real-valued signals that are derived from separate band signals that make up the input signal. The derived real signals are passed through configurable non-linear transformations, which may be adapted during operation, and which may be efficiently implemented using lookup tables. The outputs of the non-linear transformations serve as gain terms for a set of complex signals, which are functions of the input, and which are summed to compute the pre-distorted signal. A small set of the complex signals and derived real signals may be selected for a particular system to match the classes of non-linearities exhibited by the system, thereby providing further computational savings, and reducing complexity of adapting the pre-distortion through adapting of the non-linear transformations.

Multi-band digital compensator for a non-linear system

Disclosed are implementations, including a method for digital predistortion of multiband signals that includes receiving an input signal comprising multiple signal portions in different frequency bands, the input signal configured to be processed by a transmit chain, of a power amplification system, comprising at least a power amplifier that produces output with non-linear distortions, with the non-linear distortions of the transmit chain being represented using a set of basis functions derived according to a single-band model of the non-linear distortions. The method further includes performing digital predistortion on signal components derived from the multiple signal portions of the input signal using a reduced set of the basis functions that excludes at least some basis functions for at least some cross-terms resulting from a full expansion of the single-band model applied to the multiple signal portions, to produce a digital predistorted signal provided to the transmit chain.

Multi-band linearization system

Disclosed are methods, systems, devices, apparatus, media, design structures, and other implementations, including a method for digital predistortion of multiband signals that includes receiving a plurality of input signals respectively associated with multiple radio frequency (RF) bands, with the plurality of input signals occupying an input frequency span corresponding to a difference between a maximum frequency in a highest of the multiple RF bands and a minimum frequency in a lowest of the multiple RF bands. The method further includes frequency shifting at least one signal from the plurality of input signals to produce condensed shifted signals, each corresponding to a respective one of the plurality of input signals, occupying a condensed frequency span smaller than the input frequency span, and processing the condensed shifted signals, including applying digital predistortion to the condensed shifted signals.

Multiband digital predistorter

Disclosed are crest factor reduction (CFR) implementations that include a method comprising getting communication system data representative of characteristics of a communication system comprising one or more radio transmission bands, and optimizing, based at least in part on the input communication system data, a plurality of updateable parameters that determine respective pulse shapes for one or more pulses as well as other certain algorithm execution parameters for use in the CFR system. Optimizing the plurality of updateable parameters includes iteratively updating the plurality of updateable parameters based on iterative evaluation of a plurality of performance parameters. The method further includes providing the optimized plurality of updateable parameters to configure the crest reduction system for use in processing signals for radio transmission using a pulse subtraction approach applied to one or more signals communicated through the communication system.

Crest factor reduction

Disclosed are implementations, including a method comprising selecting a location of a selection buffer (that stores observed output samples produced by a signal chain) according to a pseudo-random buffer selection process, and accessing at least one observed output sample generated in response to corresponding input samples (to the system) and/or intermediary samples (outputs of a digital compensator) produced by a compensator of the system. The method further includes computing an approximation of a sub-gradient value computed according to a stochastic gradient process to derive a sub-gradient of an error function representing a relationship between the observed output sample, and the input and/or intermediary samples, computing updated values for the compensator coefficients based on current values of the coefficients and the approximation of the sub-gradient value, and replacing, at a time instance determined independently of the buffer selection process, content of part or all of the selection buffer.

Buffer management for adaptive digital predistortion

Disclosed are methods, systems, devices, apparatus, media, design structures, and other implementations, including a method that includes receiving a signal for radio transmission, and configuring crest factor reduction (CFR) processing characteristics, at a wireless device, to apply to the received signal to modify one or more portions of the signal based on an asymmetrical spectral mask, representative of an asymmetric frequency envelope limiting allowed magnitudes for frequency components bounded by the asymmetrical spectral mask, with the asymmetrical spectral mask being defined based on spectral characteristics requirements specified by multiple regulatory radio frequency (RF) power requirements at frequencies affecting a frequency range of the asymmetrical spectral mask. The method further includes applying CFR processing to the received signal according to the configured CFR processing characteristics to produce a resultant output signal with a resultant spectral representation bound by the asymmetrical spectral mask.

Spectrum shaping crest factor reduction

Disclosed are methods, systems, devices, apparatus, media, design structures, and other implementations, including a method that includes receiving a signal for radio transmission, and adjusting crest factor reduction (CFR) processing characteristics applied to the received signal to modify one or more portions of the signal according to a pre-determined spectral mask representative of a frequency envelope limiting allowed magnitudes for frequency components bounded by the spectral mask. Adjusting the CFR processing characteristics includes adjusting the CFR processing characteristics according to one or more optimization criteria for output signals generated based on the adjusted CFR processing characteristics, and subject to a constraint that the output signals generated based on the adjusted CFR processing characteristics are bound by the pre-determined spectral mask. The method further includes applying CFR processing with the adjusted CFR processing characteristics to the received signal to produce a resultant modified signal, and amplifying the resultant modified signal.

Disclosed are digital predistortion implementations, including a method that includes obtaining a first set of digital predistortion (DPD) non-linear functions for controlling operation of a digital predistorter of a wireless device operating on a received at least one input signal directed to a power amplification system comprising a transmit chain with at least one power amplifier that produces output with non-linear distortions. The method further includes determining an expanded set of DPD non-linear functions comprising the first set of DPD non-linear functions and additional one or more sets of DPD non-linear functions derived based on the first set of DPD non-linear functions and on operating condition parameters associated with operation of the wireless device, and configuring the digital predistorter with DPD coefficients determined for the expanded set of the DPD non-linear functions based on observed samples of the transmit chain responsive to the at least one input signal.

Digital predistortion in varying operating conditions

Linearization with envelope tracking or average power tracking

Disclosed are implementations that include a method comprising applying at least one input signal to a power amplification system, that includes a transmit chain with a power amplifier (PA) producing output with non-linear distortions, to produce at least one output signal, and measuring at least one observed signal of the output signal using an observation receiver coupled to an output of the transmit chain, the observation receiver having a receive bandwidth smaller than a transmit chain bandwidth of the transmit chain. Measuring the at least one observed signal includes measuring multiple frequency segments of output signal. The method further includes determining one or more sets of digital predistortion coefficients based on the measured multiple frequency segments of the at least one output signal, with each of the sets of digital predistortion coefficients being associated with a respective set of operating conditions of the power amplification system.

Subsampled linearization system

Disclosed are implementations for digital predistortion of signals provided to a radio frequency (RF) transmission path configured to transmit radio signals in a plurality of subbands within a spectral range, including a method that includes configuring a digital predistorter for predistorting signals comprising arbitrary spectral content within the spectral range. The configuring includes acquiring data samples representing operation of the RF transmission path to transmit radio signals in different subbands, each sample including a digital input signal representing spectral content concentrated in a respective subband, and updating parameters of the digital predistorter according to the acquired data samples to mitigate non-linear characteristics of the RF transmission path. The method further includes receiving a further input signal representing spectral content in a particular subband within the spectral range, and using the configured predistorter to process the further input signal to yield a predistorted signal for providing to the RF transmission path.

Growing community of inventors

Concord, MA, United States of America

Alexandre Megretski