Research On Sub-band Space-time Adaptive Anti-jamming Technology

With the continuous development and improvement of Global Navigation Satellite System(GNSS)around the world,Beidou Navigation Satellite System has been widely used in military and civilian fields.The signal power of navigation satellite is very weak and it is very easy to be interfered by the outside world.Therefore,it is very important to study the anti-jamming technology of navigation satellite signal.Space-time Adaptive Processing(STAP)can suppress interference from two degrees of freedom of Space and Time domain,which can effectively improve the anti-jamming ability of anti-jamming system.This thesis mainly studies the performance evaluation criteria involved in space-time adaptive processing technology and space-time robust beamforming algorithm,analyzes its anti-jamming performance by combining space-time robust beamforming with sub-band filtering,and tests the anti-jamming ability on a four-array anti-jamming baseband processing board in the field.1)The adaptive anti-jamming theory based on array antenna is discussed,and STAP technology and optimal beamforming criterion are analyzed.On this basis,the performance indexes and evaluation criteria of beamforming algorithm are studied,and several traditional space-time adaptive anti-jamming algorithms are analyzed.2)Aiming at the problem of Interference plus Noise Covariance(INC)matrix reconstruction algorithm,which needs to know the incoming direction of Interference signal in advance,a DOA-frequency joint estimation algorithm is proposed.The incoming direction and frequency of the interference signal are estimated.Based on the estimated prior information,the INC matrix reconstruction algorithm is extended from spatial processing to spatial time-domain processing,and the zero-notch broadening algorithm based on spatial spectrum frequency joint estimation and the zero-notch broadening algorithm based on spatial projection are simulated and analyzed to improve the robustness of the algorithm and enhance the ability of frequency domain beam control.3)A sub-band space-time filter structure is proposed by combining polyphase filter and space-time filter,and each frequency band is processed by sub-band for independent interference suppression.A kind of nearly complete reconstruction filter bank,cosine modulated multi-channel filter bank,is simulated and analyzed,and its amplitude and frequency characteristics are analyzed.The Conization of Covariance Matrix(CMT)algorithm is applied to the subband space-time filter structure,which has a more constant frequency domain characteristic while broadening the null trap.4)Engineering verification of anti-jamming algorithm on multi-array anti-jamming antenna baseband processing board is realized.Software design is studied on the basis of existing hardware platform,including high-speed serial ADC module,down-conversion and low-pass filter,adaptive anti-jamming algorithm module based on PI algorithm,automatic power control and DA module.The results of simulation and field experiment show that the base band processing board of the proposed multi-array anti-jamming antenna can filter out the compressed interference signal and ensure the accurate positioning of the rear receiver.