| This thesis sets out from the two generation methods of non-linear long periodic sequence, analyzes the correlation of the pieces of long periodic non-linear compound codes by confidence interval estimation and Massey algorithm. Based on the analysis results, this thesis summarizes two basic rules-the linear complexity of the compound codes and the correlation of the pieces of long period codes are both improved with the increase of the length of partial m sequence. And then, the general methods of the generation of long periodic non-linear codes with special characters are presented. By computer sampling the long periodic sequence and estimate the confidence interval, we can conclude the cross correlation value of long periodic sequence is biger than 0.03 with a probability lower than 10-7.This thesis also presents a new quick acquisition method of long periodic non-linear codes used in the Satellite Navigation and Positioning Signal(SNPS). To implement the SNPS acquisition, the new satellite signal frame form, modulation and error control codes are designed. The thesis originally shows a new Second-Frame structure, which is made up of the Synchronization Codes, Time Mark Codes and Pseudo-Random Codes, also brings out the spread spectrum method for the Synchronization Codes and Time Mark Codes and the analysis of the correlation and security of the pieces of the Pseudo-Random Codes in the satellite signal. This thesis presents the acquisition method of Synchronization Codes and Time Mark Codes under -20dB Gaussian channel. Then the total step length between initial state and current state can be calculated. Basing on the step length, we can deduce the current state of Pseudo-random Codes, and implement the acquisition of the special Pseudo-Random Codes. Lastly, the whole processes of satellite signal generation and acquisition are simulated by C programming. The simulation results match the analysis in theory well. |
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