適用於一位元量化Galileo 系統之PRN 碼追蹤方法

Abstract

目前大多數的定位系統中, pseudo-random (PRN)碼的追蹤的方法主要利用信號相關性函數及延遲鎖定迴路(delay-locked loop)的方法去實現.本論文利用在時域上觀測所接收的基頻Galileo信號去估計每一個信號 及 的轉變點,並利用多個信號轉變點做統計平均以達到降低雜訊的效應.接著,我們先估算每一個chip的時間長度,再利用這個資訊及多個信號轉變點以得到精確的碼差. 本論文提出兩種方法估算信號轉變點的位置,包括a)以exponential曲線及b)以線性曲線為基礎的估線方法.由模擬結果顯示,兩者皆可以達到良好的精確度.由於Galileo信號在每一週期內有許多個信號轉變點,因此我們的方法可以獲得精確的碼追蹤結果.在實際狀況下,定位誤差1個chip時間大約是差距300公尺.當訊雜比(SNR)為-20 dB的情況下,我們的方法可以達到 的chip誤差,相當於 1.6公尺的量測誤差.

Most prior and current positioning receivers use delay-locked loops based on the correlation function to perform code tracking. In this thesis, we estimate each signal transition point in Galileo signal and use the statistics of multiple signal transition points to reduce noise effect. Then, we estimate the chip duration and further use this information as well as multiple signal transitions to get accurate code phase error. We design two algorithms to estimate the signal transition points: a) an exponential curve based algorithm and b) a linear curve based algorithm. From simulation results, both methods can achieve accurate results. Because Galileo signals have many signal transition points in a code period, therefore our method can obtain accurate code tracking. In the practical environment, if code tracking error is one chip, the corresponding distance error is about 300 meters. When SNR is -20 dB, the standard deviation of code tracking error in our scheme is reduced to chip, which is about 1.6 meters in error.