Research On Fast Acquisition Algorithm Of Weak GPS BOC Signal

In the 21st century, the application of satellite navigation technology has become an integral part of life. With GPS technology application fields constantly expanding, people propose higher and higher request for GPS receiver. Receiver is divided into two types: hardware receiver and software receiver. Software receiver process base-band signal by microprocessor, when the system needs upgrade, software receiver just modify the program or the parameter, so it has flexibility operation and compatibility of the navigation system.Today's operation and under construction satellite navigation system all use a new signal modulation pattern, binary offset carrier modulation technology. Acquisition algorithm of BOC modulated signal for software receiver is urgent to be designed. In the case of signal under serious degradation, the S/N have decreased to some level. As a result of that, receiver positioning accuracy decline significantly and overall performance is so bad that it's hard to acquire and track navigation satellite signal. GPS software receiver need processing gain to obtain a suitable S/N. But computing power of GPS software receiver is lower than hardware receiver, it can't provide enough computing power to additional signal algorithm, thereby software receiver is very hard to real-timely acquire signal.In order to acquire the low SNR satellite navigation signal, the paper research on the acquisition algorithm of BOC modulated signal and the algorithm of rapidly accumulation SNR gain. Firstly, developing research on the BOC modulation techniques and analyzing the autocorrelation features, spectral features, and unique fuzzy features of BOC modulated signal. Then on the basement of the existing GPS C/A code signal, establishing the mathematical model of the modern GPS L1C civil signal, furthermore simulating and testing it. On the basement of the introduction of the basic software receiver acquisition algorithm principle, analysis a variety of BOC modulated signal acquisition algorithm. By comparing the performance, selected cross-correlation algorithm as the basement algorithm of what eliminate multi-peak feature of BOC modulated signal.As accumulation algorithm is the key technology to improve SNR, the paper start the research based on the traditional SNR accumulation algorithm, and comprehensively analysis the advantages and limitations of the various accumulation algorithm. On the basement of coherent combined differential coherent accumulation algorithm, modify correlation operation, coherent accumulation algorithm and testing variable, and propose fast SNR accumulation algorithm. Simulation results show that it can real-timely detect low SNR signal. Pointing to the characteristics of weak BOC modulated signal, the paper combine improved cross-correlation algorithm and fast accumulation algorithm to fonn a weak BOC modulated signal fast acquisition algorithm. For low SNR BOC modulated signal, the algorithm shows superior performance of real-time ability and detection ability.Finally, summarize the full-text and point out the direction of our next research as well as a new generation satellite navigation software receiver.