Wideband digital predistortion linearizer for nonlinear amplifiers

A linear wideband amplifier system, comprising:

• a nonlinear amplification chain along which a wideband input signal is upconverted and amplified for transmission;
• a multi-dimensional data structure in which each storage element stores a set of compensation parameters, including filter coefficients, for predistorting the wideband input signal;
• an addressing circuit that generates indexes for each of the multiple dimensions of the data structure, based at least upon characteristics of the wideband input signal, to read sets of compensation parameters from the data structure for use, wherein the addressing circuit generates a first index that represents an instantaneous characteristic of the wideband input signal, and generates a second index that represents an averaged characteristic of the wideband input signal, and uses the first and second indexes in combination to address the multi-dimensional data structure such that the first and second indexes correspond respectively to first and second dimensions of the multi-dimensional data structure;
• a digital compensation circuit that predistorts the wideband input signal, prior to processing along the amplification chain, using the sets of compensation parameters read from the multi-dimensional data structure, to compensate for nonlinearities in the amplification chain;
• an adaptive compensation estimator that generates the sets of compensation parameters stored in the multi-dimensional data structure based on a non-real-time analysis of signals within the amplifier system;
• and
• a feedback circuit that generates a digital observation signal which represents an output of the amplification chain, and provides the digital observation signal to the adaptive compensation estimator.

A method of predistorting an input signal to an amplifier system to compensate for distortion introduced by the amplifier system, the method comprising:

• digitally processing the input signal to generate a plurality of indices, wherein each of the indices corresponds to a different respective characteristic of the input signal;
• applying the plurality of indices in combination to a memory to look up a set of predistortion coefficients therefrom;
• and
• digitally predistorting the input signal according to the set of predistortion coefficients to compensate for distortion introduced during amplification;
• whereby the input signal is predistorted using a predistortion function that is dependent upon multiple characteristics of the input signal;
• wherein the step of digitally processing the input signal to generate a plurality of indices comprises generating a first index that represents an instantaneous characteristic of the input signal, and generating a second index that represents an averaged characteristic of the input signal.

A system for digitally predistorting a wideband input signal to a power amplifier, comprising:

• a multi-dimensional data structure in which each element stores a set of compensation parameters, including filter coefficients, for predistorting the wideband input signal to compensate for nonlinearities in an amplification process;
• an addressing circuit that generates indexes for each of the multiple dimensions of the data structure, based at least upon characteristics of the input signal, to read sets of compensation parameters from the data structure;
• a digital compensation circuit that predistorts the input signal in real time using the compensation parameters read from the multi-dimensional data structure according to the addressing circuit;
• and
• an adaptive estimation component that generates the compensation parameters, and stores the compensation parameters in the multi-dimensional data structure, based on a non-real-time analysis of the wideband input signal and an observed output signal;
• whereby a predistortion function applied by the digital compensation circuit is dependent upon the characteristics of the wideband input signal.

A system for digitally predistorting a wideband input signal to a power amplifier, comprising:

• a multi-dimensional data structure in which each element stores a set of compensation parameters, including filter coefficients, for predistorting the wideband input signal to compensate for nonlinearities in an amplification process;
• an addressing circuit that generates indexes for each of the multiple dimensions of the data structure, based at least upon characteristics of the input signal, to read sets of compensation parameters from the data structure;
• and
• a digital compensation circuit that predistorts the input signal in real time using the compensation parameters read from the multi-dimensional data structure according to the addressing circuit, wherein the digital compensation circuit comprises a quasi-static filter that is cascaded with a dynamic filter, wherein coefficients of the dynamic filter are updated more frequently than coefficients of the quasi-static filter;
• whereby a predistortion function applied by the digital compensation circuit is dependent upon the characteristics of the wideband input signal.

A system for digitally predistorting a wideband input signal to a power amplifier, comprising:

• a multi-dimensional data structure in which each element stores a set of compensation parameters, including filter coefficients, for predistorting the wideband input signal to compensate for nonlinearities in an amplification process;
• an addressing circuit that generates indexes for each of the multiple dimensions of the data structure, based at least upon characteristics of the input signal, to read sets of compensation parameters from the data structure, wherein the addressing circuit generates a third index using an output of a temperature sensor that measures a transistor die temperature of the power amplifier, and uses the third index in combination with first and second indexes to look up sets of compensation parameters from the multi-dimensional data structure;
• and
• a digital compensation circuit that predistorts the input signal in real time using the compensation parameters read from the multi-dimensional data structure according to the addressing circuit;
• whereby a predistortion function applied by the digital compensation circuit is dependent upon the characteristics of the wideband input signal.

A system for digitally predistorting a wideband input signal to a power amplifier, comprising:

• a multi-dimensional data structure in which each element stores a set of compensation parameters, including filter coefficients, for predistorting the wideband input signal to compensate for nonlinearities in an amplification process, wherein the wideband input signal has a spectral occupancy that exceeds 0.1% of the input signal's RF carrier frequency;
• an addressing circuit that generates indexes for each of the multiple dimensions of the data structure, based at least upon characteristics of the input signal, to read sets of compensation parameters from the data structure;
• and
• a digital compensation circuit that predistorts the input signal in real time using the compensation parameters read from the multi-dimensional data structure according to the addressing circuit;
• whereby a predistortion function applied by the digital compensation circuit is dependent upon the characteristics of the wideband input signal.

A linear wideband amplifier system, comprising:

• a nonlinear amplification chain along which a wideband input signal is upconverted and amplified for transmission;
• a multi-dimensional data structure in which each storage element stores a set of compensation parameters, including filter coefficients, for predistorting the wideband input signal;
• an addressing circuit that generates indexes for each of the multiple dimensions of the data structure, based at least upon characteristics of the wideband input signal, to read sets of compensation parameters from the data structure for use;
• a digital compensation circuit that predistorts the wideband input signal, prior to processing along the amplification chain, using the sets of compensation parameters read from the multi-dimensional data structure, to compensate for nonlinearities in the amplification chain, wherein the digital compensation circuit comprises a quasi-static filter that is cascaded with a dynamic filter, wherein coefficients of the dynamic filter are updated more frequently than coefficients of the quasi-static filter;
• and
• an adaptive compensation estimator that generates the sets of compensation parameters stored in the multi-dimensional data structure based on a non-real-time analysis of signals within the amplifier system.

A system for digitally predistorting a wideband input signal to a power amplifier, comprising:

• a multi-dimensional data structure in which each element stores a set of compensation parameters, including filter coefficients, for predistorting the wideband input signal to compensate for nonlinearities in an amplification process;
• an addressing circuit that generates indexes for each of the multiple dimensions of the data structure, based at least upon characteristics of the input signal, to read sets of compensation parameters from the data structure;
• and
• a digital compensation circuit that predistorts the input signal in real time using the compensation parameters read from the multi-dimensional data structure according to the addressing circuit, wherein the digital compensation circuit comprises a finite impulse response (FIR) filter for which coefficient sets are read from the multi-dimensional data structure;
• wherein the digital compensation circuit comprises a first digital filter that processes the input signal and comprises a second digital filter that independently processes a second order multiple of the input signal, wherein outputs of at least the first and second digital filters are summed to form a compensated input signal;
• whereby a predistortion function applied by the digital compensation circuit is dependent upon the characteristics of the wideband input signal.

A system for digitally predistorting a wideband input signal to a power amplifier, comprising:

• a multi-dimensional data structure in which each element stores a set of compensation parameters, including filter coefficients, for predistorting the wideband input signal to compensate for nonlinearities in an amplification process;
• an addressing circuit that generates indexes for each of the multiple dimensions of the data structure, based at least upon characteristics of the input signal, to read sets of compensation parameters from the data structure;
• and
• a digital compensation circuit that predistorts the input signal in real time using the compensation parameters read from the multi-dimensional data structure according to the addressing circuit, wherein the digital compensation circuit comprises a finite impulse response (FIR) filter for which coefficient sets are read from the multi-dimensional data structure;
• whereby a predistortion function applied by the digital compensation circuit is dependent upon the characteristics of the wideband input signal;
• and wherein the digital compensation circuit comprises:
• means for generating higher order multiples of the input signal;
• means for independently filtering the input signal and each higher order multiple of the input signal;
• and
• means for combining the input signal and the higher order multiples of the input signal after filtering to form a compensated input signal.

A linear wideband amplifier system, comprising:

• a nonlinear amplification chain along which a wideband input signal is upconverted and amplified for transmission;
• a multi-dimensional data structure in which each storage element stores a set of compensation parameters, including filter coefficients, for predistorting the wideband input signal;
• an addressing circuit that generates indexes for each of the multiple dimensions of the data structure, based at least upon characteristics of the wideband input signal, to read sets of compensation parameters from the data structure for use;
• a digital compensation circuit that predistorts the wideband input signal, prior to processing along the amplification chain, using the sets of compensation parameters read from the multi-dimensional data structure, to compensate for nonlinearities in the amplification chain;
• an adaptive compensation estimator that generates the sets of compensation parameters stored in the multi-dimensional data structure based on a non-real-time analysis of signals within the amplifier system, wherein the adaptive compensation estimator generates the compensation parameters, and stores the compensation parameters in the multi-dimensional data structure, based on a non-real-time analysis of signals corresponding to the wideband input signal and an observed output signal;
• and
• a feedback circuit that generates a digital observation signal which represents an output of the amplification chain, and provides the digital observation signal to the adaptive compensation estimator.