以可適性模糊系統補償高功率放大器之非線性效應

Compensating the Nonlinear Effect of High Power Amplifiers with Adaptive Fuzzy Systems

楊伯勳(Po-Hsun Yang)

指導教授 ： 李 穎

元智大學/工程學院/電機與資訊工程研究所/碩士(1997年)

摘要

在無線通訊系統中的非線性現象主要是由傳輸端的高功率放大器
所引起的。此非線性裝置常會造成QAM調變訊號的扭曲效應(warping
effect)，進而嚴重影響傳輸品質。此外，在傳輸端還有因符際干擾所
引起的訊號點散開效應(clustering effect)。為了有效的消除傳輸端中
warping effect與clustering effect，本論文將使用於基頻操作的data
predistorter作為所需的補償器。在predistorter中所使用的nonlinear
filter，常見的有多項式型態的Volterra series與多層神經網路。而本論
文將使用可適性機率模糊推論系統來進行基頻資料預扭曲的非線性補
償。並分別在model free與model based兩種架構下設計predistorter。
我們發現fuzzy predistorter與只具奇數項且包含complex conjugate的
Volterra series predistorter有類似的性能。而fuzzy predistorters的優點
是在於選取可調參數之初值時，較Volterra series predistorters容易。

關鍵字

放大器 ； 非線性 ； 補償器 ； 預扭曲 ； 可適性 ； 模糊

並列摘要

Nonlinear effects of wireless communication systems are mainly due to
the high power amplifier in the transmitter. The high power amplifier is a
nonlinear device. The warping effect caused by the high power amplifier
will seriously degrade the transmission quality of QAM modulated signals.
Furthermore, the clustering effect caused by intersymbol interference will
also affect signal quality. In order to suppress warping effect and clustering
effect, one possibility is to use data predistorter operating at baseband as a
compensator. The nonlinear filters commonly used in the predistorters are
polynomial-type Volterra series filters and neural networks. In this thesis
we use adaptive probabilistic fuzzy inference systems CFBFN(Complex
Fuzzy Basis Function Network) for baseband data predistortion. We
propose two fuzzy predistorters based on model free and model based
design methods, respectively. We discover that fuzzy predistorters and
Volterra series predistorters with odd order and complex conjugate terms
have similar performance. The advantage of fuzzy predistorters is that the
initial values of adjustable parameters are easier to obtain compared to the
Volterra series predistorter.

並列關鍵字

Amplifier ； Nonlinear ； Compensator ； Predistortion ； Adaptive ； Fuzzy

參考文獻

[1] M. Schetzen, The Volterra and Wiener Theories of Nonlinear Systems. New York: Wiley, 1980.

[2] A. A. M. Saleh, "Frequency-independent and frequency-dependent nonlinear models of TWT amplifiers," IEEE Trans. Commun., vol. COM-29, pp. 1715-1720, Nov. 1981.

[3] J. Tsimbinos and K. V. Lever, "Computational complexity of Volterra based nonlinear compensators," Electron. Lett., vol. 32, pp. 852-854, Apr. 1996.

[4] C. Eun and E. J. Powers, "A new Volterra predistorter based on the indirect learning architecture," IEEE Trans. Signal Processing, vol. 45, no. 1, pp. 223-227, Jan. 1997.

[5] M. Ghaderi, S. Kumar and D. E. Dodds, "Adaptive predistortion line-ariser using polynomial functions," IEE Proc.-Commun., vol. 141, no. 2, pp. 49-55, Apr. 1994.