US 6,476,670 B2 · Amplifier measurement and modeling processes for use in generating predistortion parameters

Abstract

A wideband predistortion system compensates for a nonlinear amplifier's frequency and time dependent AM—AM and AM-PM distortion characteristics. The system comprises a data structure in which each element stores a set of compensation parameters (preferably including FIR filter coefficients) for predistorting the wideband input transmission signal. The parameter sets are preferably indexed within the data structure according to multiple signal characteristics, such as instantaneous amplitude and integrated signal envelope, each of which corresponds to a respective dimension of the data structure. To predistort the input transmission signal, an addressing circuit digitally generates a set of data structure indices from the input transmission signal, and the indexed set of compensation parameters is loaded into a compensation circuit which digitally predistorts the input transmission signal. This process of loading new compensation parameters into the compensation circuit is preferably repeated every sample instant, so that the predistortion function varies from sample-to-sample. The sets of compensation parameters are generated periodically and written to the data structure by an adaptive processing component that performs a non-real-time analysis of amplifier input and output signals. The adaptive processing component also implements various system identification processes for measuring the characteristics of the power amplifier and generating initial sets of filter coefficients. In an antenna array embodiment, a single adaptive processing component generates the compensation parameters sets for each of multiple amplification chains on a time-shared basis. In an embodiment in which the amplification chain includes multiple nonlinear amplifiers that can be individually controlled (e.g., turned ON and OFF) to conserve power, the data structure separately stores compensation parameter sets for each operating state of the amplification chain.

Claims26

Dependent claims

A method of generating a model of a wideband amplifier, comprising:

applying narrowband stimulation signals to the amplifier over a plurality of amplitude levels and a plurality of center frequencies, and using resulting amplifier output data to compute amplitude-dependent and frequency-dependent variations in at least the gain and phase rotation introduced by the amplifier;
applying a wideband stimulation signal to the amplifier, and using resulting output data to compute bulk estimates of at least the gain, phase rotation and delay introduced by the amplifier;
generating a data structure which contains multiple sets of finite impulse response (FIR) filter coefficients indexed by signal amplitude level, wherein the FIR filter coefficients incorporate the amplitude-dependent and frequency-dependent variations in the gain and phase rotation;
and
cascading a bulk stage that incorporates the bulk estimates of the gain, phase rotation and delay with a filter stage that filters an input signal using the FIR filter coefficients stored in the data structure, wherein the filter stage selects sets of FIR filter coefficients from the data structure for use based at least upon a current amplitude of the input signal.

2 more elements

Dependencies are inferred from the claim text.

Amplifier measurement and modeling processes for use in generating predistortion parameters

Life of this patent

Amplifier measurement and modeling processes for use in generating predistortion parameters

Life of this patent

Abstract

Claims26