Study On Intra-Pulse Repeater Jamming Suppression Methods With Time-Frequency Domain

Modern radar systems face an increasingly complex electromagnetic jamming environment,and the application of digital radio frequency memory in electronic confrontation allows jammers to generate deceptive jamming which is highly similar to the target echo in the multi-dimensional domains of space,time,frequency and polarization.Indeed,it can lead to appear false targets,and the radar detection performance will be severely deteriorated even complete failure.Owing to the maturity of self-defense jamming and the emergence of clustered cooperative jamming,the possibility of deceptive jamming entering from the mainlobe will be increased,and traditional methods of sidelobe cancellation are difficult to work.With the development of high-speed digital signal processing technology,the deceptive jamming will be released by jammer within the current pulse repetition interval of intercepted transmitted radar signal,referred to as intra-pulse repeater jamming,which will disable the radar using waveform diversity technology.To this end,a novel method of suppressing intra-pulse interrupted-sampling repeater jamming is developed by using the difference between targets and jamming in the time-frequency domain,while a hardware measured system is also built to verify the superior performance of the proposed method.The main work can be summarized as follows:1.The difference between the target echo and interrupted-sampling repeater jamming in the time/frequency domain is exploited to study three methods for the suppression of jamming in the time/frequency single-dimensional domain.Firstly,the operating principle of the DRFM jammer and the signal model of various interrupted-sampling repeater jamming are introduced.Then the characteristics of the jamming in the time/frequency domain and the results of pulse compression are analyzed by computer simulation.Secondly,the implementation processes of three jamming suppression methods are illustrated,and computer simulations verify the effectiveness of the methods.Finally,the evaluation index of jamming suppression effect is introduced,and the anti-jamming performance of the methods is studied.The results of Monte Carlo experiments show that the over-threshold zeroing method with time-domain is prone to cause expected signal loss when the jamming delay is small or the signal-noise ratio is close to the jamming-noise ratio.In the case of a low signal-noise ratio(SNR),the time/frequency domain filtering method will result in the construction of a filter with a reduced sidelobe compression ratio,poor jamming suppression or even failure,and a serious deterioration in performance.2.Focusing on the problem that the performance deterioration significantly of the single-dimensional methods under the low SNR and the limited discrimination with single-dimensional domain information results in the loss of the desired signal,combining instantaneous time-frequency curve extraction based on Viterbi algorithm with time-frequency filtering,a novel jamming suppression method is proposed,referred to as Viterbi-TFF method.Firstly,two methods of time-frequency curve extraction are introduced.After a comparative analysis of the performance of the methods,the Viterbi algorithm can ensure the continuity of the time-frequency curve.Secondly,based on the results of time-frequency curve extraction,a jamming slice bandwidth estimation method using the connected component features is proposed.Then,the ideas and steps of the proposed jamming suppression method are described in detail.Finally,the effectiveness of the proposed method is verified by computer simulations,and the performance of the four methods is compared.Monte Carlo experiment results show that the proposed method has more stable performance and maintains good jamming suppression capability at a low SNR and the signal-to-jamming ratio improvement factor characterizing the anti-interference performance remains above 19.2 d B,which is better than that of the time/frequency single-dimensional domain jamming suppression method.3.Based on the team’s self-developed radar anti-jamming hardware platform,the timing generation module,power supply and receive gain control module on the timing board,the UDP communication module,SRIO communication module and channel correction module on the receiving board have been designed and developed independently,and the hardware platform has been relied on to carry out several field jamming countermeasures.Firstly,the overall system scheme and the functions of each subsystem are described in detail.Next,the block diagrams of the timing board and receiving board subsystem structure are introduced respectively,while the pre-layout simulation and test verification results are also given.Finally,an outfield jamming countermeasure test scenario and procedure are designed,and the effectiveness of the proposed jamming suppression method is verified by the processing and analysis of multiple sets of measured data.