Robust Anti-jamming Techniques For Global Navigation Satellite System

Global navigation satellite system could provide real-time, all-weather and globalnavigation services for land, sea and air, which has been widely used in civil andmilitary applications and has been become one of the fastest developing informationindustries. However, the receiver is extremely vulnerable to intentional andunintentional radio frequency interferences because the received satellite signal is farlower than the noise. When the power of interference exceeds the spreading gain offeredvia the global navigation satellite system, the receiver will be unlock the satellite signal,which lost its ability to navigate. This dissertation is mainly concerned with the robustanti-jamming techniques for satellite navigation based on the array antenna. Theauthor’s major contributions are outlined as follows:1. The suppression technique for multiple kinds of interference coexistence hasbeen studied. A unified anti-jamming algorithm for deception interference, blanketjamming and satellite multipath interference is proposed based on the known thedirection of arrival (DOA) of satellite signal. Firstly, the correlation property of GPSsignal and deception interference is analyzed and the corresponding method is appliedto estimate interference subspace according to the different correlation property.Secondly, the interferences are canceled by projecting the received signal onto theinterference orthogonal complement space. Finally, satellite multipath interference ismitigated by low sidelobe conventional beamforming and also the mainlobe of the beampattern is aimed to the direction of the satellite signal. The proposed algorithm is robustfor the type of interference and simulation results show the effectiveness of the newmethod.2. The adaptive anti-jamming algorithm based on the DOA estimation has beenstudied. Firstly, the interferences are suppressed by projecting onto the interferenceorthogonal complement space. Then, according to the period repetitive property ofspread code, the cross-correlation vector between the projected data and the perioddelay data is used to estimate the directions of the satellite signals by CLEAN algorithm.Finally, the multi-beam is formed by estimated directions. The proposed algorithmcould solve the problem that interference suppression algorithm by using directly theperiod repetitive property can not satisfy the requirement of position. And the newmethod will also work well even if the number of array elements is less than the numberof GPS signals, therefore it is robust for the number of satellites. Test data andsimulation results show the effectiveness of the new algorithm. 3. The blind adaptive anti-jamming technique has been studied. The new de-spreadre-spread algorithm based on the characteristic of satellite signal is proposed. The newmethod is firstly discussed in the spatial processing, and then extended to space-timeadaptive processing. The proposed algorithm could also estimate the directions ofsatellite signal. Therefore it provides directly the direction information of equalizationrequirement in space-time processing. Firstly, the interferences are suppressed byprojecting onto the interference orthogonal complement space. Then requisition andtracking are performed for the signal of projected reference antenna, and the satellitesignal is reconstructed by tracking result. Finally, the array weight vector is calculatedby the cross-correlation vector between the reconstructed satellite signal and theprojected signal. Therefore, the new algorithm is tight coupling to the conventionalreceiver and is easy for engineer realization. The new method is not need to estimateDOAs of satellite signals and is robust because the proposed method is not sensitive forthe number of satellite signals and array error. Test data and simulation results show theeffectiveness of the proposed algorithm.4. High dynamic GPS interference suppression algorithm has been studied. In highdynamic environment, the conventional adaptive beamforming technique could nottrack the rapid change of interference directions due to the narrow nulls. Therefore, arobust widenull algorithm is proposed combing the null broadening technique withrobust beamforming technique. The new method could improve the performance androbustness of the conventional null broadening beamformer for snapshot deficient inhigh dynamic environment. Simulation results have demonstrated the performance ofthe new method.