A fast adaptive predistorter for nonlinearly amplified M-QAM signals

Author

Besbes, H. ; Le-Ngoc, T.

Author_Institution

Dept. of Electr. & Comput. Eng., McGill Univ., Montreal, Que., Canada

Volume

1

fYear

2000

fDate

2000

Firstpage

108

Abstract

M-QAM has been considered to achieve high bandwidth efficiency for broadband wireless communications. However, due to its envelope fluctuation, it exhibits large spectral re-growth and performance degradation when the transmit power amplifier operates in a nonlinear region close to saturation. In this paper, an adaptive predistortion technique suitable for DSP implementation at the baseband signals is introduced to counter-balance the AM/AM and AM/PM nonlinear effects of the transmit power amplifier. Based on nonlinear adaptive Volterra filtering, the proposed pre-distortion technique shows that M-QAM can be used with a transmit power amplifier operating near saturation to a highest power efficiency, while its transmitted spectrum and performance are kept close to those in a linear channel. The convergence behavior of the adaptive predistortion technique is analyzed. The spectral re-growth and performance of a 16 QAM system using a predistorter/SSPA are evaluated using simulation. The adaptive predistortion technique has a low complexity and fast convergence

Keywords

adaptive filters; adaptive signal processing; broadband networks; computational complexity; convergence of numerical methods; electric distortion; filtering theory; nonlinear filters; power amplifiers; quadrature amplitude modulation; radio networks; radiofrequency amplifiers; 16 QAM system; AM/AM nonlinear effects; AM/PM nonlinear effects; DSP implementation; adaptive predistortion; baseband signals; broadband wireless communications; convergence behavior; fast adaptive predistorter; fast convergence; high bandwidth efficiency; linear channel; low complexity method; nonlinear adaptive Volterra filtering; nonlinearly amplified M-QAM signals; performance degradation; power efficiency; predistorter/SSPA; simulation; spectral re-growth; transmit power amplifier; transmitted spectrum; Bandwidth; Broadband amplifiers; Broadband communication; Convergence; Degradation; Digital signal processing; Fluctuations; Power amplifiers; Predistortion; Wireless communication;

fLanguage

English

Publisher

ieee

Conference_Titel

Global Telecommunications Conference, 2000. GLOBECOM '00. IEEE

Conference_Location

San Francisco, CA

Print_ISBN

0-7803-6451-1

Type

conf

DOI

10.1109/GLOCOM.2000.891706

Filename

891706