Study On Jamming Technique Against SAR Based On Micro-motion Characteristic

Synthetic Aperture Radar (SAR) with Ground Moving Target Indication (GMTI)capability has increasingly become an important means of strategic reconnaissance andbattlefield surveillance systems, poses a sever threat to important military targets.Therefore the jamming technology for countering SAR/GMTI has become an importantnew issue in Electronic Counter Measure (ECM) area. A method against SAR andGMTI is introduced which is based on the micro-Doppler phenomenon that takes placewhen ISAR observes a micro-motion target, and a jamming technology imitatingmicro-motion is basically formed.In the beginning, the background and significance of this research subject areillustrated, and the present status of SAR ECM techniques, including SAR system andjamming evaluation techniques are introduced. The types, development history,development trend and existing problems of SAR jamming techniques are especiallyanalyzed. The present status of SAR/GMTI jamming techniques is further summarized.The major research efforts of this dissertation are also explained.Based on observation vector model, two time-frequency models in Doppler domainare separately established by investigating two typical kinds of micro-motion targetswhich are uniform rotation and vibration. The models are more accurate than preciousstudies. It is proposed that the micro-Doppler differences among various micro-motionscan provide SAR/ISAR some new features for target recognition. The simplifiedDoppler models are summarized and the simplified conditions are analyzed accordingtypical SAR observation status.Starting with the simplest situation that a stationary bulk with only onemicro-motion scatter center, other3situations are all analyzed, that are bulk translation,multiple micro-motion scatter centers and micro-motion across range cells duringimaging time. Imaging features are obtained for each circumstance. Next, consideringthe Doppler history difference between micro-motion objects and real targets thatdistribute along azimuth direction, defocusing phenomenon is analyzed which results inrange migration correction, and constrains are given to avoid defocusing. The potentialof rotating reflectors deployed as a passive jammer is demonstrated by an airborne SARexperiment. Finally, the potential of a micro-motion type jammer to interference SARautofocus is qualitative analyzed, taking an instance of Mapdrift autofocus.Three well-known GMTI technologies based on multi-antennae are taken intoaccount, micro-motion targets’ amplitude and phase characters are analyzed in eachGMTI method. Results show that micro-motion modulation has an ability to interfereGMTI. It turns out that the micro-motion modulation interference will still work onFrFT technology. The micro-motion analogy jamming technology is proposed based on upperresearch. Power demand is analyzed in the first place. The parameters adjustmentpolicies are concluded considering different jamming effects and jamming objects. Also,in order to extend the jamming energy to cover range direction, the micro-motionanalogy jamming combined with fixed noise samples is proposed, which is named“azimuth coherent noise” style. The jamming effects are shown with a example whichmodulates noise samples by frequency modulation. For military protection of fixedpositions, the article also provides a simplified method of reconnaissance, by a networkcomposed with several reconnaissance equipments with low performance requirements.This method can achieve the task to pilot a jammer.On the basis of concluding existing objective evaluation methods, some improvedobjective evaluation methods are presented. By means of implementing human visualsystem (HVS) models and contrast sensitivity function (CSF), those current objectiveevaluation methods can somehow reflect subjective feelings of human eyes. Thisadvantage is improved by some simulations presented in this paper. This paperconcludes with how to use HVS characteristics to pretreat envelope fluctuation alongrange direction, and how to use FFT-based approach to modulate pretreated profile.Simulation results indicate that the performance of azimuth coherent noise interferenceis improved.In the end, this paper summarizes the research work and main innovations, anddiscusses the future work to be researched.After all, the novel suppressing jamming based on micro-Doppler is effective andfeasible in practice, which has four prominent advantages. Firstly the micro-motionmodulation jamming signal can be processed partially coherently in azimuth, which canmake up for the jamming inferiority in processing gains. Secondly its jamming effectcan be improved both in anti-detection and visual observation by optimizing rangerepeating signal. Thirdly it has weak dependency on reconnaissance systems, especiallywhen protecting a fixed position; it can guide jammers with a network assembling byseveral simple reconnaissances. Fourthly it allows for interfere GMTI, and can protectthe stationary and moving targets simultaneously. While studying the jammingtechnique, this thesis approaches another two achievements. One is to amendmentnowadays micro-Doppler models under SAR observation, and the simplificationconditions are given. Furthermore, it implies that thoes micro-Doppler differences maybe the features to be extracted to distinguish various micro-motions. The otherachievement is the presentation of SAR jamming assessment indexies based on humanvisual system. These enriche the SAR jamming effect evaluation methods. Themicro-motion modulation jamming technique constructed in this dissertation, not onlyenriches the electronic countermeasure theory, but most promisingly improves thesurvivability of important ground military targets against SAR/GMTI, which has an important meaning in national defense.