應用於GPS/Galileo衛星導航訊號追蹤迴路之設計與分析

Abstract

全球導航衛星系統(GNSS)，乃泛指所有提供空間定位的衛星導航系統。自2007年來，美國的NAVSTAR全球定位系統(GPS)是目前唯一完整操作的全球衛星導航系統(GNSS)。在開始部署階段歐盟的伽利略定位系統，即將是下一個全球衛星導航系統(GNSS)。其完成的時程，預計在2010年。 伽利略系統所使用的訊號架構為BOC(Binary Offset Carrier)調變。BOC調變是將附載波乘上展頻碼，其頻率為碼率的倍數。伽利略的調變方式和全球定位系統的調變方式不一樣，所以對於伽利略的訊號，我們需要新的追蹤演算法。在這篇論文中，我們討論了兩個伽利略訊號追蹤演算法。 追蹤是基頻訊號處理的一部分，再接收機中有三個追蹤迴路，其分別為載波相位追蹤迴路、載波頻率追蹤迴路及碼追蹤迴路。在這篇論文我們分析了這些追蹤迴路。雜訊頻寬為追蹤迴路中最重要的參數。在這篇論文中，我們描述如何去決定最佳的雜訊頻寬。接著我們討論了一些射頻效應。

Global Navigation Satellite System (GNSS) is the standard generic term for satellite navigation systems that provide autonomous geospatial positioning with global coverage. As of 2007, the United States NAVSTAR Global Positioning System (GPS) is the only fully operational GNSS. The European Union’s Galileo positioning system is a next generation GNSS in the initial deployment phase, scheduled to be operational in 2010. Galileo system employs modern signal structure and modern BOC (Binary Offset Carrier) modulation. A BOC modulation multiplies a spreading code with a square wave sub-carrier that has a frequency multiple of the code rate. It is different from GPS signal modulation. We need some new tracking algorithm for Galileo signal. In this thesis, we discussed the two methods for Galileo signal tracking. Tracking is the part of the baseband signal processing. The carrier phase tracking loop, the carrier frequency tracking loop, and the code tracking loop are the three tracking loops in receiver. We analyse them in this thesis. The noise bandwidth in the tracking loop is the most important parameter. We described how to determine the optimal noise bandwidth. And then, some RF effects are discussed in this thesis.