Researches On Radar Waveform And Technique Of Polarization Active Anti-jamming

The digital radio frequency memory(DRFM)repeat jammer,which can transmit signals of close signature to real target returns,is known as a typical low-cost electronic attacker and poses threats to radar systems.Hence,it is of great significance to study the radar antijamming technologies.As a new type of radar,multiple input multiple output(MIMO)radar has a special advantage to counter repeat jammer with good waveform diversity.Therefore,it makes sense for MIMO radar to counter the jammer by the waveform design.Based on the problems mentioned above,this thesis studies the anti-jamming technology for MIMO radar.The anti-jamming ability of MIMO radar is improved by waveform design,and the improvement is evaluated.The main contents are as follows.1.Basic radar anti-jamming theories are introduced.Firstly,some common methods for waveform design are reviewed.Then,the support vector machine(SVM)classifier is introduced,which can reduce the requirements of the sample size.2.A waveform design method for MIMO radar is studied,and the anti-jamming performance is evaluated.Firstly,the differences between the transmit waveforms in the spatial direction(angular waveform)and the jamming signals transmitted by DRFM-based repeat jammers are analyzed.Then,a waveform design criterion to suppress mutual correlation between the angular waveforms and the jamming signals is established to reject DRFM-based repeat jammers,which can be solved by using sequential quadratic programming(SQP)algorithm.Secondly,for signals passing the decision threshold,a classification algorithm,which is specific to limited sample problems,is evoked to examine whether it is a jamming signal or a real target return.The training samples are theoretical target returns and theoretical constant-modulus jamming signals,both modulated with different Doppler frequencies.Finally,it is verified by simulation that waveform design can improve the classification performance.3.A waveform design method for polarimetric MIMO radar is further studied,and the antijamming performance is evaluated.Firstly,the differences between the angular waveforms and the jamming signals transmitted by DRFM-based repeat jammers are analyzed.The waveform design criterion is established according to the waveforms from the horizontal and vertical polarization channels of the radar receiver,one can optimize polarimetric MIMO radar waveforms to magnify the difference between jamming signals and real targets.Secondly,for signals passing the detection threshold,we examine the classification performance improvement achieved by using the SVM method,which has a good classification effect for finite samples.Finally,the simulation results show that the waveform design can effectively improve the anti-jamming performance of polarimetric MIMO radar.