以模糊可適性網路實現數位波束形成

Fuzzy Adaptive Network For Digital Beamforming

張堯棟(Yau-Donq Jang)

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(1995年)

摘要

可適性天線陣列中，陣列訊號之合併(signal combination)傳統稱為波束
形成。波束形成的目的乃是使想要接收的訊號方向增益最大，並使得其他
方向之干擾訊號和雜訊的影響降至最低。在基頻使用數位訊號處理方法來
實現波束形成者稱為數位波束形成。傳統的波束形成器乃是直接將接收訊
號做一線性組合，得到輸出；但是當系統含有非線性成分或訊號非高斯時
，線性方法並不能獲得最佳解。本篇論文以二種模糊可適性網路─
CANFIS(Complex Adaptive-Network-Based Fuzzy Inference System)及
CFBFN(Complex Fuzzy Basis Function Network)作為非線性波束形成器
的核心演算法則，並與用RLS(Recursive Least Square)方法調整參數之
線性波束形成器於線性及非線性訊號環境進行性能比較。本文以數位行動
通訊系統為例，採用QPSK等效基頻訊號進行模擬，並使用了時間參考訊號
來訓練波束形成器的參數。模擬結果顯示非線性模糊波束形成器在線性訊
號環境的性能表現和線性波束形成器類似，且對非線性失真現象能有效克
服。當系統有非線性現象時，模糊波束形成器可以有效提昇陣列天線之空
間多工性能，有助於增加行動通訊系統之容量。

關鍵字

模糊 ； 波束形成 ； 可適性 ； 天線陣列

並列摘要

In adaptive antenna arrays, the combination of array signals is
usually referred to as "beamforming". The goal of beamforming is
to maximize the directionalgain of the desired signal and
attenuate the interference and noise arriving from other
directions. The output of a conventional beamformer is the
linear combination of the array received signals. If the system
contains nonlinear terms or the signals are non-Gaussian,
however, optimal solutions cannot be obtained by linearly
combining the received signals. In this thesis, we use two kinds
of fuzzy adaptive networks ---- CANFIS(Complex Adaptive-Network-
Based Fuzzy Inference System) and CFBFN(Complex Fuzzy Basis
Function Network) as the nonlinear beamforming algorithms, and
compare the performance with the linear beamformer using RLS(
Recursive Least Square) method for parameter tuning both in the
linear and nonlinear signal environment. We consider a wireless
digital mobile communication system and use equivalent baseband
QPSK signal for simulation. The beamformer parameters are
trained by temporal reference signals. From the simulation
results, the performance of the fuzzy adaptive networks is
similar to that of the linear beamformer in the linear
environment, and is superior in the nonlinear environment. Fuzzy
nonlinear beamformers can better explore the spatial diversity
of antenna arrays, especially when system nonlinearityis
present.

並列關鍵字

fuzzy ； beamforming ； adaptive ； array