The Analysis On The GPS Receiver's Acquisition And Tracking Performance Under Suppressing Interference

In the war of navigation, usage of the GPS has become essential for precise command control and the precision of attacks and armed force deployment and influence the means and effects of the war at its every phase. Interference on the GPS can not only disrupt the precision of attacks by stealth planes, cruise missiles and other warplanes, warships, and tanks, but also the coordination among them during the war. So reasearch on the theory and technology of the GPS interference has become the urgent task for the Chinese army. This paper focused on analyzing the GPS receiver's acquisition and tracking performance under suppressing interference. After analysis on the GPS communication system's property of direct sequence spread spectrum, this paper conclude: the GPS' C/A code receiver and P code receiver have a spread spectrum gain of 43dB and 53dB. So they have the anti-interference ability to a certain degree. This paper deduced a detailed mathematical model for signal acquisition and tracking based on the analysis of the GPS receivers' circuit. After deducing the expression formula for the probability of signal detection and false alarm under the acquisition state, this paper calculated the average accquistion time and its variance; and also calculated the timing error variance under the tracking state. Based on the above results, this paper performed the simulation using Matlab tools under the suppressing interference. The results indicate that: firstly, single frequency interference has a better interference effect than narrowband interference, and narrowband interference has a better effect than broadband interference; secondly, despite the fact that the GPS receiver has certain anti-interference capability, when the interference power reaches certain level, the GPS receiver can not acquire and tracking the signal normally. The results provide the theoretical basis for analyzing the effect of suppressing interference of the GPS receiver and the evaluation of choices of interference mode.