最小頻寬短碼直接序列展頻訊號

Abstract

在本篇論文中研究可實現最小奈奎斯(Nyquist)頻寬短碼直接序列展頻訊號 (Short Code Direct Sequence Spreading Spectrum Signals) 之執行可行性及訊號之時間旁波(Temperal Sidelobe)特性。提出的短碼直接序列展頻訊號為限頻且可實現，不像傳統限頻短碼直接序列展頻訊號使用方均根餘弦(Square-Root Raised Cosine)濾波器需要消費額外的頻寬。我們提出一廣義限制保證短碼直接序列展頻訊號可以實現，且使用之短碼顯示出時間旁波隨著|t|^(-K-1)之速率快速衰減，其中K是一個與展頻碼有關的非負整數參數。基於此一廣義限制，存在的短碼包括沃爾什哈達碼 (Walsh Hadamard, WH Codes)、正交互補格雷碼(Orthogonal Complementary Golay, OCG Codes)、複利葉轉換碼(Discrete Fourier Transform, DFT Codes)與修改式扎德朱碼(Modified Zadoff-Chu, Modified ZC Codes)被評估為實現可行性就最小奈奎斯頻寬直接序列展頻訊號方面。最後，本篇論文亦分析可實現訊號格式使用沃爾什哈達碼、正交互補格雷碼、複利葉轉換碼與修改式扎德朱碼及相關時間旁波衰減速率特性可完全由其引數 (Code Indices) 來描述。

In this thesis, short-code direct-sequence-spreading-spectrum (DSSS) signals occupying minimum Nyquist bandwidth are investigated in terms of implementation feasibility and associated with the analysis of the property of temporal sidelobe decaying. The proposed short-code DSSS signals are bandlimited and realizable without consuming any excess bandwidth, as is required in traditional bandlimited short-code DSSS signals using the square-root raised cosine (SRRC) pulse shaping. A general constraint on short code is developed to guarantee that a short-code DSSS signal is realizable and exhibits fast-decaying temporal sidelobes which decay asymptotically as |t|^(-K-1), with K being a positive-integer-valued design parameter. Based on the constraint, existing short codes including Walsh-Hadamard (WH), orthogonal complementary Golay (OCG), discrete Fourier transform (DFT), and modified Zadoff-Chu (ZC) codes, are evaluated for realization feasibility in terms of the minimum-Nyquist-bandwidth DSSS signaling format. It is analytically shown that the realizable signaling formats using WH, OCG, DFT, and modified ZC codes and the corresponding temporal sidelobe decaying properties can be completely described by their code indices.