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Predistortion control

A predistortion and predistorter technology, applied in the direction of compensating for predistortion by memory effect, improving amplifiers to reduce nonlinear distortion, amplifiers, etc., can solve problems such as predistorter performance deterioration and predistorter performance limitations.

Inactive Publication Date: 2005-09-07
ANDREW CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The performance of AM-AM and AM-PM type predistorters as described above is limited when linearizing an amplifier exhibiting memory since only that component of the distortion can be corrected as a function of the instantaneous signal amplitude
[0005] Generally speaking, the amplifier memory effect will become more and more significant as the signal bandwidth increases, so the performance of traditional AM-AM and AM-PM predistorters will be correspondingly worse

Method used

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Embodiment Construction

[0028] The basic building blocks of a state-of-the-art predistorter are shown in figure 1 middle. This form of predistorter often operates with the aid of two look-up tables (for example, to adjust the gain and amplitude of the input signal to the amplifier) ​​that are retrieved as some function of the signal amplitude, or the input amplitude , which then acts to modify the amplitude and phase of the signal applied to the input of the amplifier in order to counteract its distortion. However, this form of predistorter only corrects for amplifier distortion that varies with the instantaneous amplitude of the input signal. Such distortions are commonly referred to as AM (amplitude modulation) to AM and AM to PM (phase modulation) distortions, and are referred to herein as transient distortions.

[0029] Unfortunately, many real amplifiers exhibit distortion that varies with past and present signals, and these amplifiers are said to have a "memory". When linearizing an amplifie...

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Abstract

A digital predistorter comprises a module J for producing a counteracting signal Vm1 for combination with the input signal of a power amplifier to correct the output of the amplifier for distorting memory effects within the amplifier. The module J produces the counteracting signal Vm1 by convolving (see Figure 6) functions of the input signal with impulse response characteristics related to the memory effects being corrected. The counteracting signal Vm1 is produced by a function fm and parameters in that function are adjusted to minimise any residual distortion in the amplifier output.

Description

technical field [0001] The present invention relates to apparatus and methods for controlling a predistorter operating on an input signal to a signal processing apparatus, such as a power amplifier in a mobile radiotelephone, in order to reduce the signal in an output signal generated in response to the input signal. The amount of distortion caused by the processing device. Background technique [0002] Predistorting power amplifier input signals is well known in the digital domain. Digital predistorters have been found to be increasingly useful in linearizing RF (radio frequency) power amplifiers, due in part to the recent availability and enabling of high sampling rate analog-to-digital converters (ADCs) and digital-to-analog converters. A corresponding increase in the speed of digital signal processing (DSP) hardware made this form of linearization possible. It is also due to the increasing use of non-constant envelope modulation schemes and the even greater need to inc...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H03F1/32
CPCH03F2201/3224H03F1/3247
Inventor 安东尼·J·史密森
Owner ANDREW CORP