全數位基頻直接序列展頻接收器之設計

Abstract

在基頻直接序列展頻(DSSS)接收器的設計中, 碼同步(code synchronization)是一個重要的部分。這篇論文主要研究目的在探討在QPSK調變及加成性白色高斯雜訊(AWGN)下, 全數位基頻非同調碼追蹤迴路(noncoherent code tracking loop)的穩態性能。我們同時討論了接收器其它相關子系統之設計。我們分析並模擬了所提出的載波相位估計及碼相位鎖定偵測器之性能, 找到適當的參數並證明其可行性。另外, 量化的影響, 內差濾波器及本地基頻波形的選擇也都有說明。 最後, 我們將上述各種實際的因素列入模擬的考慮, 從而估計出位元錯誤率的大小, 證明我們的設計的確可滿足一般系統的規格要求。

In direct-sequence spread-spectrum receiver design, code synchroni- zation is an important part. The main purpose of this thesis is to investigate the steady state tracking performance of a all digital baseband noncoherent code tracking loop in the presence of additive white Gaussian noise (AWGN). We also consider issues related to the designs of subsystems. These practical concerns include the effect of ADC (quantizer), the selections of interpolation filter and local code pulse shape, the design of code tracking lock detector and carrier phase recover. Proper solutions are provided for these concerns. We give either analytical or simulated estimations of the corresponding numerical performance. The bit error probability performance of the overall receiver is given, taking all the above practical and nonideal effects into account. Numerical results show that our design is indeed appropriate for meeting the system specifications.