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Study Of Radar Anti-jamming For Active Deception Jamming

Posted on:2018-05-30Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y L LuFull Text:PDF
GTID:1362330542492941Subject:Signal and Information Processing
Abstract/Summary:PDF Full Text Request
As an all-weather information sensing equipment in the modern battlefield,radar has become the core equipment in the field such as battlefield reconnaissance and surveillance,target recognition,munitions guidance,cooperative operation of all kinds of soldiers and so on.Because of the importance of the radar on the battlefield,it has been subjected to a wide variety of electronic countermeasures(ECM)since its advent.With the maturity of digital radio frequency memory(DRFM)technology,ECM seeking to develop radar active deception jamming which has flexible jamming patterns.Radar active deception jamming can accurately simulate radar echo signal,and the jamming can enter the radar system from the antenna main lobe with low power,which make the ability to survive in the battlefield of the radar poses a huge threat.And with the continuous development of ECM technology,more active deception jamming styles with specific interference effects have been proposed;it also puts forward a new challenge to the modern radar's ability to perceive the disturbance environment and the ability of anti-interference.In order to deal with the huge threat of radar active deception jamming to radar system,in particular,the active deception jamming from the main lobe of the radar antenna,and improve the ability of anti-active deception jamming of radar,the work mechanism and interference characteristics of typical active deception jamming pattern based on DRFM are analyzed in this dissertation.Combining the modern signal processing algorithms,the research on the sensing and suppression of radar active deception is carried out.The main results can be summarized as follows: 1.In view of the fact that the active jamming signal comes from the main lobe of the radar antenna does not need very large transmit power,and in the case of the failure of the conventional energy detection methods,a novel jamming detection approach is outlined based on time-frequency domain entropy feature.The main work is as follows: the phase sampling quantization jammer system is analyzed firstly,then the harmonics are extracted through the empirical mode decomposition(EMD)algorithm,and a time-frequency entropy statistic,which has the precious property of a constant false-alarm rate(CFAR),is designed to describe the energy distribution diversity in time-frequency domain between the jamming harmonics and target echo when both of them are co-existent in a range gate.Actually,at the gate capture period of gate pull off type jamming(range gate pull off,velocity gate pull off,range gate and velocity gate combined pull off),in order to capture the radar distance/velocity gate,the jammer will only amplify the intercepted radar signal,and send back to radar without modulation.In this dissertation,the proposed method can effectively detect the deception jamming signal at this period so that the radar system can take anti jamming measures in time.2.Based on the previous work,and aiming at the detection problem of the linear frequency modulation(LFM)active deception jamming that comes from the main lobe of the radar antenna,a novel approachis outlined based on LFM rate matching of the jamming harmonic components.The main work is as follows: digital quantization characteristics of DRFM in phase sampling,leads the active deception jamming signal generate a series of LFM harmonic signals,and the center frequency of the harmonic signal component and its modulation frequency are obviously different from the real target echo.Then a LFM rate base of the jamming is established.Then the fractional fourier transform(FRFT)is employed to detect LFM components in radar echo when both target echo and jamming signal are co-existent in a range gate.After that the LFM rates of the detected LFM signal are estimated and are compared with the LFM rate bank to achieve jamming detection.The method can effectively detect the active deception jamming signal in the complex electromagnetic environment.Validity of the method is verified by simulation results.3.The active jamming from the main lobe of the radar antenna is similar to the target signal both in the time domain,the frequency domain,the energy domain and the direction of arrival,which makes the conventional interference suppression methods invalid.According to the digital quantization characteristics of the DRFM system,the quantized jamming model is build first.Then a novel anti-jamming approach is proposed based on singular spectrum analysis(SSA).In the actual jammer system,the time delay function that modulated by the DRFM system is not ideal and nonlinear,which leads the RGPO signal's spectrum has a slightly different center frequency from the input radar signal and generates the spurious signal components.The main work is as follows: First,the singular values energy distribution diversity between jamming harmonics and target echo,which have been pretreated through SSA decomposition,is extracted for jamming detection based on a CFAR detection statistic.Then according to the center frequency diversity,a suitable subspace of singular values is divided for recovering the target echo,which means the jamming is mitigated simultaneously.The proposed approach does not need to estimate noise parameter,and has the precious CFAR property in the jamming detection stage.4.In view of the suppression of the new spectral smeared spectrum(SMSP)jamming,a novel anti-jamming approach is proposed based on jointing time-frequency(TF)distribution and compressed sensing(CS).The SMSP jamming is a special active deception jamming that from the main lobe of the radar antenna for countering the LFM pulse compression radar system,which acts as dense false targets in the radar display terminal.The main work is as follows: In the time-frequency domain,the time-frequency distribution of the SMSP and the target signal are partially overlapped.First the SMSP jamming is isolated in the TF domain,and then the TF points belong to target signal are reserved.According to the linear relationship between the reserved TF points and the frequency domain of radar echo,a CS minimization problem model is established and the orthogonal matching pursuit(OMP)algorithm is utilized to recover the target signal,which means the SMSP jamming is mitigated simultaneously.The validity of the proposed method is evaluated using experimental data via Monte Carlo simulation.5.In order to solve the problem that the SMSP and C&I two type dense decoy,this dissertation proposes a new sensing method based on the characteristics in the time-frequency domain of a pulse.Firstly,one-dimensional interference signal is translated to two-dimensional time-frequency domain using synchrosqueezing transform(SST)time-frequency rearrangement method to improve the readability of the time-frequency image,and at the same time image segmentation strategy is adopted to reduce the computational load according to the frequency edge entropy of time-frequency image.Then the high order moments and texture features are extracted based on the segmented time-frequency image and the SVM classifier is used to realize the two kinds of the interferences.The feasibility of the method is verified by simulation data.
Keywords/Search Tags:radar anti-jamming, radar active deception jamming, jamming detection, jamming sensing, jamming suppression, time-frequency analysis, constant false-alarm rate
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