Research On GPS Anti-jamming Technologies

The paper focused on the key technologies of the anti-jamming unit between antennas and GPS receiver.Since satellite navigation systems have already been used widely, the ways to improve their anti-jamming capability become an emergent task. The paper majors in anti-jamming technologies of GPS. The traditional technologies are not as good as enough because each of them can only treats limited kinds of interferences. Space-Time adaptive processing technology (STAP) shows great predominance in interferences elimination. Almost all kinds of interferences can be counteracted by STAP technology. Since the degrees of freedom in anti-jamming capability are increased, STAP technology performs a very important role in GPS interferences elimination. However, the computational burden of STAP increases enormously along with the improvement of anti-jamming capability. To deal with the problem, a reduced-rank algorithm is needed. In the dissertation, a simplified multistage nested wiener filter (MWF) was presented in chapter 2. The simplification on forward recursion of MWF was implemented. As a consequence, the cost on computation decreased greatly. The results of simulations certified it.Multipath effect is another major source of GPS error besides interferences. The usual ways used in CDMA systems can not be utilized in GPS systems. The technologies employed in GPS are also restricted by physical and electromagenetic circumstances. The dissertation presents two different ways to deal with the multipath effect in chapter 3. Each of them was designed for one specific situation. Finally, the simulation results were presented.Since the interferences and multipath effect both can deteriorate the performance of GPS receivers, it is crucial to study the anti-jamming technology under the circumstances with multipath effect. The dissertation showed two designs of GPS receivers in chapter 4. One of them was of low complexity and designed for the condition that the electromagnetic circumstance changing fast. The other was of higher complexity and designed for the condition that the electromagnetic circumstance that never chang or change slowly. Its performance was comparatively better than the former. Both methods were proved by the simulations.Nowadays, an electronic facility can not be used alone. There are many kinds of them are active in the same time. The coexistence of GPS with other digital systems needs more attention then. The dissertation analyzed the problems of GPS receivers caused by narrowband digital systems,wideband CDMA systems and UWB (Ultra-Wide Band) systems, which leads to the conclusion that MUD (Multiuser Detection) was an efficient way to solve the coexistence of these systems. Additionally, a way to eliminate MAI in GPS systems was discussed in chapter 5. Its capability was proved by the simulation results.During the reception of GPS signals, the jitter of clock is caused by the electromagnetic circumstance or the bad performances of electronic elements. As a result, the BER of the systems deteriorate greatly. The dissertation analyzed the effect of jitter theoretically and presented a mathematical expression of the effect in chapter 6. Also simulation results were shown. The results can be useful for technical utilization.