The Research Of Correlation Coefficient Applied On The GPS Receiver

No matter what Global Navigation Satellite System is, in essence it’s a Spread Spectrum Communication System based on Code Division Multiple Access technology, such as the GPS, BeiDou, Galileo and etc. In the satellites end, in order to make that the different satellites can broadcast its own navigation message on the same frequency carrier without interference happens, they spread and modulate the transmitted signal with their own Pseudo Random Code. Then, in the receiver end, it will be needed to synchronize all the available satellite signal to fulfill despreading and demodulating the received signal. And generally this is performed in the acquisition and tracking stages beyond the signal flow of a receiver. When a receiver acquisitions and tracks the received signal, one of the core section is the correlation between the received signal and a copy of the Pseudo Random Code which is accomplished in a correlator based on the autocorrelation function. On one hand, the autocorrelation function checks the similarity between input signal and its time delay version. On the other hand, a correlator Based on the autocorrelation function is equivalent called the matched filter whose demonstration and design are carried out under the hypothesis that the environmental noise is only the additive Gaussian white noise. But the satellite signal could be confounded with other noise, such as the impulsive noise. Inspired by these two aspects, the research of this paper is taken as follows.Firstly, since the correlation coefficient is served as a tool which quantifies the strength of statistical relationship between two signals, then we introduce the correlation coefficient to be metrics to the correlation of the Pseudo Random Code. The robustness properties of five correlation coefficients and the matched filter are analyzed. Monte Carlo simulations not only verify our analytical results, but also reveal the advantage of SR, KT, GC and PRVCC which deal with the interference of impulsive noise.Secondly, in a radar, sonar or GNSS receiver, in order to obtain a fast and real-time signal correlation processing, the realization of the correlator is usually in the form of hardware. For this reason, several signal detection circuits of correlation coefficient are proposed in this paper.Thirdly, with the C/A code as the experimental object, feasibility that correlation coefficient served as metrics to auto-correlation and cross-correlation of the Pseudo Random Code. Both acquisition algorithm and tracking loop which would be employed to a software-defined GPS receiver are designed based on correlation coefficient, then the GPS signal which is collected with the RF front-end in the western 11 building attic of Guangdong University of Technology will be post-processed in that GPS receiver. Reliability of the GPS receiver based on correlation coefficient is proved by analyzing the results of acquisition, tracking and position calculation.Finally, both the theoretical analysis and simulational result prove reliability of signal correlation detection based on correlation coefficient, meanwhile the innovative research work of this paper will provide an alternative for the design of GPS correlator.