Active Deceptive Jamming Against SAR Based On Convolutional Modulation

Synthetic Aperture Radar(SAR), having drastically developed during last decades, is widely applied in military fields. Consequently, jamming techniques against SAR have received increasingly intensive attention in recent years. This thesis researches on SAR deceptive jamming techniques based on convolutional modulation, especially on the matched convolutional modulation method in respect of fast generation of jamming signal and of the effects of parameters estimation errors on jamming, and on Doppler-shift convolutional modulation method in respect of the effective region. The thesis consists of five chapters, the contents of which are arranged as following:Chapter 1 introduces the background and significance of the thesis, presents the status of the researches on jamming techniques against SAR, among which the active decetpive jamming by repeater jammer is particularly emphasized. The framework of the thesis is also pointed out in this chapter.Chapter 2 expounds the basic concepts and fundamental principles. SAR imaging as well as active deceptive jamming against SAR based on convolutional modulation method is firstly introduced. Jamming methods based both on matched convolutional modulation and on Doppler-shift convolutional modulation are explained theoretically.Chapter 3 faces the difficulty in how to produce real-time jamming signals for jamming method based on matched convolutional modulation. A novel frequency-domain three-stage algorithm(FDTSA) is proposed, which effectively accelerates the modulation process of a repeat jammer and, at the same time, gets rid of severe focus deterioration of the false scatterers. Two existent fast algorithms, the direct frequency algorithm and the two-stage algorithm, are introduced and analyzed. The FDTSA proposed is studied in detail in terms of theoretical principles, implementation scheme, computational complexity and parameters criteria, etc. Simulations on false point scatterer, extended false scene and scattered false targets are provided to verify the effectiveness of the FDTSA. The works of this chapter especailly avail to forge extended false scene and scattered false targets, and to drastically reduce the cost of a jammer.Chapter 4 considers the actual condition that jammer cannot exactly estimate the parameters of SAR, and analyzes the effects of parameter estimation errors on the jamming method based on matched convolutional modulation. The models of SAR platform position errors are established, and the jamming signal on the condition that parameter estimation errors are present is formulated. By comparing the echoes of a moving target and the jamming signal, we disclose the equivalent motion effect induced by parameter estimation errors. That is to say, parameter estimation errors make the jamming signal resemble echoes of a moving target. The works of this chapter avail the analysis of jamming effect, widen the flexibility of the protection of moving targets, and may also promote the anti-jamming.Chapter 5 concentrates on the effective region of the jamming method based on Doppler-shift convolutional modulation. After the mathematical analysis of the difference between jamming signal and a real point-target echo, we point out that residual Range Cell Migration(RCM), matched filter error and loss of Doppler bandwidth are three main factors that lead to the deterioration of the focus of a jamming signal. Furthermore, the formulation of the effective region by the criterion of focus quality is obtained by theoretical analyses and verified by simulation results. The study indicates that the false scatter can be well focused only when it is in close proximity to the jammer, thus that the method can effectively protect limited regions around the jammer.