A Nonlinear Distortion Compensation Method with Adaptive Predistorter and Negative Feed-Back for a Narrow-Band Signal

Yitao ZHANG  Osamu MUTA  Yoshihiko AKAIWA  

Publication
IEICE TRANSACTIONS on Communications   Vol.E91-B   No.7   pp.2331-2337
Publication Date: 2008/07/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e91-b.7.2331
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Wireless Communication Technologies
Keyword: 
nonlinear distortion compensation,  negative feedback,  adaptive predistorter,  convergence speed,  stability,  

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Summary: 
The adaptive predistorter and the negative feedback system are known as methods to compensate for the nonlinear distortion of a power amplifier. Although the feedback method is a simple technique, its instability impedes the capability of high-feedback gain to achieve a high-compensation effect. On the other hand, the predistorter requires a long time for convergence of the adaptive predistorters. In this paper, we propose a nonlinear distortion compensation method for a narrow-band signal. In this method, an adaptive predistorter and negative feedback are combined. In addition, to shorten the convergence time to minimize nonlinear distortion, a variable step-size (VS) method is also applied to the algorithm to determine the parameters of the adaptive predistorter. Using computer simulations, we show that the proposed scheme achieves both five times faster convergence speed than that of the predistorter and three times higher permissible delay time in the feedback amplifier than that of a negative feedback only amplifier.