Fixed-Point Conjugate Gradient Digital Pre-Distortion (DPD) Adaptation

Abstract

A predistortion method and apparatus are provided which use a DPD actuator (225) to apply a memory polynomial formed with first DPD coefficients to a first input signal x[n], thereby generating a first pre-distorted input signal y[n] which is provided to the non-linear electronic device (253) to produce the output signal, where the memory polynomial may be adaptively modified with a digital predistortion adapter (224) which computes second DPD coefficients u[n] with an iterative fixed-point conjugate gradient method which uses N received digital samples of the first pre-distorted input signal y[n] and a feedback signal z[n] captured from the output signal to process a set of conjugate gradient parameters (u, b, v, r, ω, α, β) at each predetermined interval, thereby updating the first DPD coefficients with the second DPD coefficients u[n] generate a second pre-distorted input signal which is provided to the non-linear electronic device.

Description

BACKGROUND OF THE INVENTION[0001]Field of the Invention[0002]The present invention is directed in general to field of information processing. In one aspect, the present invention relates generally to digital predistortion for compensating an input signal for distortion introduced to the input signal by an electronic device.[0003]Description of the Related Art[0004]Wireless communication devices, such as mobile devices and base stations, typically include transmitter and receiver circuits (i.e., transceivers) in which power amplifiers are used to amplify a signal before wireless transmission to another device. However, some radio frequency (RF) power amplifiers generate out-of-band spurious emissions or otherwise add non-linear distortion to the amplified signal, where the distortion may include, for example, variations in phase differences and / or variations in amplitude differences. Significant distortion may result in poor signal quality. Traditional approaches for meeting the out-...

AI Technical Summary

Problems solved by technology

However, some radio frequency (RF) power amplifiers generate out-of-band spurious emissions or otherwise add non-linear distortion to the amplified signal, where the distortion may include, for example, variations in phase differences and / or variations in amplitude differences.

Significant distortion may result in poor signal quality.

Traditional approaches for meeting the out-of-band spurious transmission requirements would operate the power amplifier well below its maximum output power, or require very expensive and inefficient power amplifiers which are designed according to the maximum peak power that they have to handle.

In many cases, this process results in effective cancellation of the distortion (i.e., the non-linearities) produced within the system, and a more linear output signal may result.

In any case, the real-time processing requirements for evaluating a polynomial and updating the DPD coefficients to track changes in the power amplifier performance can impose significant complexity and processing costs in terms of the significant digital processing resources required to evaluate the polynomial.

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