| Synthetic aperture radar(SAR)offers a unique opportunity of remote sensing with all-day,all-weather,long-range,and high-resolution imaging capability.Having many unique advantages compared with visible light imaging,infrared imaging,and laser imaging,SAR is widely used in military reconnaissance,intelligence search,battlefield surveillance,attack guidance,operational effectiveness evaluation and many other fields.As SAR has been developing rapidly in recently years and applied to more and more areas,jamming techniques against SAR,especially the deceptive jamming against SAR,have drawn much attention in the field of electronic warfare(EW)and electronic countermeasures(ECM).The objective of this thesis is to study the large-area deceptive jamming against multi-mode high-resolution SAR.The study contents of the thesis mainly consist of four aspects,including 1)the theoretical foundations,2)the jamming algorithm design,3)the implementation techniques,and 4)the performance analyses of jamming.With purpose of supporting the design,the fulfillment,and the application of jammer against SAR,the main contents of this thesis are as follows.1.The theoretical foundations of large-area deceptive jamming against multimode high-resolution SAR.The thesis studies the characteristics of SAR echo,and then,the physical principle of deceptive jamming against SAR.Jammer is modelled as a linear system,and the mathematical model of jammer modulation function is established.In addition,the intelligence gathering requirement is analyzed.It is pointed out that deceptive jamming against SAR requires the estimate of three kinds of radar parameters,including the kinematic parameters of radar platform,the transmitted radar signal parameters,and radar antenna parameters.2.The algorithm design for large-area deceptive jamming against multi-mode high-resolution SAR.Three fast parallel algorithms are proposed to calculate the jammer modulation function parallelly and efficiently.Firstly,the jamming objective is assumed as a stripmap SAR with ideally linear trajectory,and an inverse Omega-K algorithm is proposed.The inverse Omega-K algorithm reformats jammer modulation function and calculates jammer modulation function by operations including fast Fourier transform(FFT),chirp-z transform / Stolt transform,and complex multiply,etc.The computational efficiency,computational accuracy,the flexibility and validity limit of large-area deceptive jamming against SAR are significantly improved by the Omega-K algorithm.For existing efficient algorithms for large-area deceptive jamming against SAR,only SAR with zero or small squint angle and moderate resolution can be considered,and the range magnitude of false scene is limited.The inverse Omega-K algorithm overcomes the problems mentioned above.Then,the jamming objective is extended as multimode SAR with ideally linear trajectory,and an acquisition mode mutation method is proposed.By applying bandpass filtering to jammer modulation function,the proposed method can change the SAR acquisition mode corresponding to jammer modulation function,and obtain the jammer modulation function for multiple acquisition modes,such as terrain observation with progressive scan(TOPS)mode,staring spotlight mode,and sliding spotlight mode,etc.For the moment,existing efficient methods for large-area deceptive jamming against SAR are valid only for stripmap mode SAR,and the proposed method breaks through such limit.Last,the jamming objective is further extended to multimode SAR with trajectory deviation,and a trajectory mutation method is proposed.In the proposed method,SAR transfer function is modelled as a spatial function of radar location,and it is disclosed that the spatial spectrum of SAR transfer function is band limited.Based on the Nyquist sampling theorem,the proposed method obtains jammer modulation function for SAR with trajectory deviation by interpolating a collection of jammer modulation functions for SAR with ideally linear trajectory.For the moment,existing efficient methods for largearea deceptive jamming against SAR are valid only under condition that radar moves along an ideally linear trajectory,and the proposed method breaks through the limit.3.The implementation of large-area deceptive jamming against multi-mode high-resolution SAR.The implementation of large-area deceptive jamming against multimode high-resolution SAR is studied,and a implementation technique based on offline computation and online mutation is proposed.By innovating the implementation tactics,the proposed technique overcomes the restrict that jammer can not begin to work until accurate information of radar parameters is obtained by intelligence gathering.For the first time,it points out the possibility of offline computation under condition that accurate information of radar parameters is absent.As the technique transfers as much computational complexity to the offline stage before jammer obtains the accurate information of radar parameters,the computational burden that should be coped with in online stage can be drastically reduced.In addition,theoretical analyses and simulation results shows that the technique can also alleviate the conflict between computational efficiency and computational accuracy,flexibility and validity limit.The advantages and limits of the method is discussed when it is applied to spaceborne SAR and airborne SAR.4.The performance analyses of large-area deceptive jamming against multimode high-resolution SAR.The thesis mainly studies the robustness analysis of deceptive jamming against SAR,and the jammer transmitter power analysis of deceptive jamming against SAR.Firstly,the robustness of deceptive jamming against SAR is analyzed.For the moment,there are many qualitative analyses on the robustness of deceptive jamming against SAR,but there is a lack of quantitative analyses.In the manner of quantitative analysis,the thesis studies the influence of the inaccuracy of intelligence gathering,especially the estimate errors of kinematic parameters of radar platform,on the effect of deceptive jamming against SAR.It is pointed out that,when the estimate of kinematic parameters of radar platform are inaccurate,jamming signal is equivalent to the real radar echo of certain ground moving target.Based on such an equivalent relationship,we propose a method for quantitatively analyzing the feature of false targets in SAR image domain based on the feature of ground moving target.The study can not only be used to guide the design of the intelligence gathering subsystem,but also can serve as a foundation of optimizing jamming configurations and optimizing the robustness of jamming.Then,the jammer transmitter power of deceptive jamming against SAR is analyzed.The thesis is devoted to comparing the jammer transmitter power between deceptive jamming and barrage noise jamming against SAR.It is pointed out that,in order to yield same jamming-to-signal ratio in SAR image domain,the ratio of the transmitter power of incoherent noise jamming to that of coherent deceptive jamming should be the average pulse compression gain(APCG)defined in this thesis,rather than the pulse compression gain(PCG)in SAR image formation processing as believed by some literatures.The study can serve as an instruction for scheduling jammer transmitter power. |
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