Rf power amplifier system employing an analog predistortion module using zero crossings
AssigneePowerwave Technologies, Inc.
InventorRichard Braithwaite
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Abstract
An RF amplifier system employing an analog predistortion module is disclosed. The disclosed analog predistortion module is based on zero crossings of the gain error curves (AM-AM and AM-PM curves minus DC). The hardware structure uses the product of first-order functions avoiding the need for large differential swings in the coefficients to shape the lower part of the gain curves. The higher-order nonlinear functions are preferably derived from a single envelope detector. An equal number of multipliers are preferably used in each path when the order of the magnitude and phase corrections are equal or differ by one, thus reducing delay mismatches between the magnitude and phase correction signals.
Claims20
A linearized power amplifier system, comprising:
- an input receiving an analog communication signal;
- a main signal path comprising a power amplifier, and a delay circuit and a vector modulator coupled between the input and the power amplifier;
- an output coupled to the output of the power amplifier;
- a signal splitter coupled to the input and providing a sampled input signal on a parallel signal path to the main signal path;
- and
- an analog baseband predistortion module configured in the parallel signal path and receiving the sampled input signal, the analog baseband predistortion module performing an analog predistortion operation employing the sampled input signal and zero crossing coefficients characterizing nonlinearity in the amplifier gain response and providing in phase and quadrature predistortion control signals to the vector modulator in said main signal path to predistort the input signal to correct for amplifier nonlinearity.
A linearized power amplifier system, comprising:
- an input receiving an analog communication signal;
- a main signal path comprising a power amplifier, and a delay circuit, a gain adjuster and a phase adjuster coupled between the input and the power amplifier;
- an output coupled to the output of the power amplifier;
- a signal splitter coupled to the input and providing a sampled input signal on a parallel signal path to the main signal path;
- and
- an analog baseband predistortion module configured in the parallel signal path and receiving the sampled input signal, the analog baseband predistortion module performing an analog predistortion operation employing the sampled input signal and zero crossing coefficients characterizing nonlinearity in the amplifier gain response and providing a gain adjuster control signal to the gain adjuster in said main signal path and a phase adjuster control signal to the phase adjuster in said main signal path to predistort the input signal to correct for amplifier nonlinearity.
A method for predistortion linearization of a power amplifier system comprising:
- receiving an input communication signal;
- splitting the input communication signal into a main input signal and a sampled input signal;
- providing the main input signal to a power amplifier;
- detecting the sampled input signal envelope;
- generating predistortion control signals using the product of first-order functions of the sampled input signal envelope offset by zero crossing coefficients;
- and
- applying the predistortion control signals to the main input signal prior to said amplifier to predistort the main input signal to compensate for nonlinearities in the power amplifier gain response.
Dependencies are inferred from the claim text.