Research On VHF Radar Anti-jamming Method Based On Adaptive Filter

VHF radar frequency is 30MHz~300MHz,and its wavelength is 1m~10m.VHF radar wavelength is longer,so it has perfect characters of anti-ARM and anti-stealth ability.There is still a certain ability to detect the target below the sight or behind the shelter(trees,etc.)which is in the radio wave shadow zone.Based on the above features,VHF radar becomes one of the key direction of air intelligence radar.Along with the vigorous development of the military offensive and defensive tactics,modern radar electronic jamming style is diverse,flexible and strong antagonism,so it brought serious challenges to VHF radar anti-jamming technology.Especially when the interference is wide-band interference or false-target interference,the traditional narrow-band adaptive filter is severely degraded.The traditional adaptive filtering algorithm is difficult to fight a complex interference,so it was improved in this paper to solve the problem that it does not apply to broadband signal,and change the situation that it can only be effective to suppress the noise interference and be unable to suppress the false target interference.Finally,the new method improves anti-jamming performance of VHF radar array.The main work of this paper is as follows:(1)When the jamming signal is a wideband signal,the time delay cannot be ignored.Therefore,the narrow-band adaptive beamforming cannot effectively suppress the interference.In this paper,a wideband adaptive beamforming method is used to suppress the interference.The method is validated by simulation and experimental data processing.(2)It is difficult to obtain the training sample which does not contain the target signal to construct the covariance matrix,and when the traditional adaptive filtering method is used to eliminate the interference,it will form a zero settlement in the target direction.On the other hand,traditional adaptive filtering is applicable in relatively stable interference environment.However,false target jamming change relatively quickly and the adaptive beam formation is unable to obtain good learning samples or enough time to learn.So,it is unable to obtain the optimal adaptive weight vector,and the beam pattern cannot form a beam nulling with sufficient depth in the direction of interference.The result is leading to anti-jamming performance degradation.A new method for thereconstruction of the covariance matrix based on the DOA angle measurement is studied in this paper.With the result of interference signal and the target signal DOA estimation,the new method constructs the interference covariance matrix and the adaptive weight vector to realize zero setting in the direction of interference.So it can counter false target jamming effectively.The correctness and effectiveness of the technique are verified by simulation.