多重路徑衰減通道上直接序列展頻接收器中載波頻率回復之研究

Abstract

我們要設計一個行動無線通訊系統時, 必先瞭解信號傳送通道的特性。當 車輛速度增快時, 都卜勒效應可能導致接收器無法正確地鎖住載波頻率 。 本論文將著眼於行動無線通訊多重路徑衰減通道中, 直接序列展頻接 收器載波頻率回復之設計。在此提出兩種載波頻率回復的方法:一種是線 性化平方迴路 (Linearized Squaring Loop), 另一種是自動頻率控制迴 路 (Automatic Frequency Control Loop)。我們將以理論及模擬的角度 來比較這兩種方法。 In designing a mobile radio communication system, we first need to know the characteristics of the associated communication channel. High vehicle speed causes large Doppler frequency shift and may end up in loose lock of frequency in a mobile radio receiver. This thesis focuses on the design of carrier frequency recovery methods for a direct sequence spread spectrum receiver in a multipath fading channel for mobile radio communications. We propose two methods for carrier frequency recovery, one is a lineari zed squaring loop (SL) and the other is an automatic frequency control (AFC) loop. We compare these two methods from both theoretic and simulation points of view.