Research On Anti-jamming Technology Applied On The GPS Software

In the modern war, satellite navigation plays a very important role,and dominates most of theintelligent weapons and navigation guidance wepon systems. In recent years, however, all previouslocal wars have exposed that the weak satellite navigation signal is vulnerable to the enemy’sintentional interference/cheating in the bad geomagnetic conditions or complicated geography combatarea, leading to problem of GPS receiver which cannot work normally. The thesis studies the GPSreceiver anti-jamming/anti-cheating technology and puts forward a set of GPS software receiverwhich realizes active disturbance rejection.Firstly, the structure of satellite navigation signal is analyzed.Mathematical formulas are derivedand simulated based on the GPS signals down-conversion, capture,tracking and navigation calculatingreceiving process. The thesis accomplishs the implementation of the C/A code and the GPS signalsimulation. Then we analyze the advantages and disadvantages between the GPS software receiverand the hardware receiver,providing theoretical basis of the GPS software receiver anti-jammingtechnology for the later chapters.Secondly, the thesis studies Wavelet de-noising algorithm combined with differentially coherentintegration to track siganals. According to the situation that the GPS signal is vulnerable to the effectsof cover and interference outside, the sensitivity of GPS receiver capturing weak signals is nothigh.We analyzes the relationship between signal SNR and receiver siganal detectionprobability/false-alarm probability in the GPS signal capture process.To avoids the jump of navigationdata we put forward coherent integration combined with non-coherent integration. The algorithmavoids the jump of navigation data through coherent integration combined with non-coherentintegration, and then using wavelet de-noising to overcome the problems of reducing effect of filterwhen signal and noise overlap each other. Lastly based on fast Fourier transform,the simulation showsthis algorithm is very useful for weak signal.Finally, the principle of GPS retransmitted spoofing is analyzed in details. A new algorithmcalled weighted-estimate tightly integrated navigation system is presented through inertial navigationassisted GPS receiver to eliminate the interference of deception signals making bigger position error.We argue that ease of implementation and more accurate estimation features of the new filterrecommend it’s use in applications.