Research on the Direct Acquisition Search Technique for P Code in Frequency Domain Based on the Local Sum Ratio for GPS Receiver
Jianhua Zhu · Acta Geodaetica et Cartographica Sinica · 2010
CDMA is adopted to identify different satellites and measure distance by GPS receiver.GPS receiver need trace,despread/demodulate the received satellites signals and get the navigation text.At least three satellites will be needed to locate object's place by GPS receiver.The key technology to realize the GPS receiver includes generating and capturing PN code(such as C/A code and P code)and realizing some location algorithm.The precise time measurement of C/A code or P code is the key to measure distance precisely and get navigation text.C/A code which is short can be searched directly and is used to measure distance coarsely.Whereas P code which is too long to be searched directly and is used to measure distance precisely.The direct acquisition search technique for P code is divided into time domain method and frequency domain method.The latter is more efficient compared to the former.The frequency domain method includes the XFAST(Extended replica folding acquisition search technique)method and mean value method.The characteristics of the above methods are studied carefully in the paper.The direct acquisition search technique for P code based on the local sum ratio is put forward to in the paper.Some results are discussed in the paper.