使用數位訊號處理器實現抗干擾CDMA接收器

Abstract

近年來單晶片數位訊號處理器頗為盛行。結合了軟性無線電訊以及軟体為基礎的無線電訊，使用單晶片數位訊號處理器，具有可以做為快速實現的工具、低成本雛形開發、可程式化等优點。在民用通訊中，單晶片數位訊號處理器一般作為驗證演算法用，而且有許多的通訊應用，但是大多數偏重在語音、影像等。直到最近，眾家廠商推出了許多的單晶片數位訊號處理器作為GSM基頻收收器的解決方案。一個眾所周知的應用是，使用在美軍通訊系統，SMART。[9]. CDMA 有許多廣為人知的特性例如:軟性的容量，抗干擾的能力，解決多路徑傳輸、避免被竊聽。特別是在衛星通訊的應用上，CDMA技術有長久的歷史與發展。因此，我們使用單晶片數位訊號處理器實現了一個衛星地面台線性接收器。一般而言衛星通訊的主要議題在於非線性傳輸，而我們的實作則偏重在線性接接器部分，主要包含了抗干擾設計、碼同步設計、基頻接收器。這個實作包含了兩個主体: QPSK接收器與DPSK接收器。

Recently, the application of single-chip DSP is widely prevalent. Combining the idea of soft radio and software based radio, the DSP implementation has the advantages of easily development, quick realization, low cost on prototype, and programmable. In many civil communication applications, the DSP implementation is suitable for examining the developing algorithms. There were also many applications of single-chip DSP on communication system but mostly for speech or image applications. Until recently, there are DSP solutions for GSM baseband system. In military communication systems, the DSP chip is more applicable for its programmable ability. A widely known application is the SMART Radio Network for US Army[9]. Code Division Multiple Access (CDMA) system is also well known for its features: inherent capabil- ities in rejecting jamming and interference, discriminating multipath and avoiding eavesdropping. The CDMA system was ?rstly applied in satellite communication system. In this thesis, we design a system for satellite ground receiver. The main issue on satellite ground receiver is usually the non-linear e?ect. However, our receivers are concentrated in the linear receiver and show that the capabilities in rejecting narrow band interference could be enhanced by ?ltering it out. We leave the non-linear part behind for other preceding front-end. This thesis is mainly concentrated upon the anti-narrow bandinterference (NBI) design on QPSK and DPSK receiver. Those base band receivers are capable of code tracking, carrier phase recovering, decision, demodulation and anti-NBI filtering. We will introduce the basic CDMA system and the anti-NBI design. Furthermore, the realization consideration of our applied DSP would discuss. Finally the result of our realization would be presented.