Design and Verification of Algorithms on Acquisition of Weak GPS Signals
Date Issued
2005
Date
2005
Author(s)
Chen, An-Bang
DOI
en-US
Abstract
GPS is the system combined CDMA code and trilateration method to get precision positioning system. The main goal of this thesis is design and analysis of GPS receivers on acquisition and tracking of weak signals. Acquisition of weak GPS signals has some problems, such as long operation time and the probability of cycle slip will be increased. If the signals have large Doppler shift, the central frequency of signals will be changed in the integration period. When the situation happens, using the original acquisition process will get nothing. Here a new method called code delay compensation algorithm is designed. The algorithm can help the receiver to solve the problem. Besides these, two acquisition schemes will be compared, namely conventional and Fast Fourier Transform (FFT). And peak finding algorithm used on autocorrelation function will be discussed. The expectancy of the algorithm is increasing the acquisition efficiency. In order to simulate the whole system in an efficient way, all functions are simulated in the personal computer. The receiver is designed to use in indoor environment, so the power of the simulated GPS signal is only -155dBm Watt (-185 dB Watt). The power is equal to one thousandth of outdoor signal. Using the algorithm, whole system’s processing gain can be increased about 10dB. Although the algorithm is needed the aiding signal, it can catch the GPS signal correctly in the badly environment such as weak signal, strong noise and large Doppler shift.
Subjects
基頻衛星導航系統接收機
搜尋微弱信號
延遲碼補償演算法
baseband GPS receiver
acquisition of weak signal
code delay compensation algorithm
Type
thesis