Study On Motion Modulation Jamming Techniques Against SAR-GMTI

Synthetic Aperture Radar (SAR) plays an important role in strategic reconnaissance and surveillance. SAR-GMTI (Ground Moving Target Indication) can obtain the focused stationary target images and moving target information at the same time, and can form a detailed overall situation map of the battlefield, which makes it a severe threat for important military moving targets. The jamming technology for countering SAR-GMTI has already become an important new subject in electronic countermeasure (ECM) area. Based on the motion modulation effects for imaging radars, motion modulation jamming techniques against SAR-GMTI are profoundly studied.Chapter 1 illustrates the background and significance of this research subject, and introduces the present status of SAR ECM techniques, including SAR system, SAR anti-jamming and jamming evaluation techniques. The types, development history, development trend and existing problems of SAR jamming techniques are especially analyzed. The present status of SAR-GMTI system and jamming techniques are further summarized. The major research efforts of this dissertation are also explained.Chapter 2 analyzes the motion modulation effects for imaging radars. The investigated subjects are four typical kinds of moving targets with uniform motion, uniformly accelerated motion, uniform rotation and harmonic vibration. Using the stationary phase principle, the imaging characteristics and feature extraction methods of moving targets based on Stepped Frequency Radar (SFR), as well as the echo features, one-dimensional and two-dimensional image characteristics of moving targets for SAR are analyzed in detail. For the two typical imaging radar systems, SFR and SAR, the effects of target motion on the radar images are profoundly analyzed in the fast time domain and in the slow time domain respectively. The research in this chapter forms the theoretical basis of the study on motion modulation jamming techniques against SAR-GMTI.Chapter 3 studies the motion modulation jamming against SAR-GMTI based on motion modulation effects. Firstly, the jamming performance of coherent jamming and noncoherent jamming are compared from the aspect of SAR jamming equation. Then the motion modulation jamming principle against SAR-GMTI based on motion modulation effects is proposed; passive and active implementation approaches are pointed out; the active motion modulation jamming models of four typical kinds of moving targets are built respectively; key jamming parameters are determined; and the effects of reconnaissance errors on jamming images are analyzed. Moreover the countering effects against GMTI and the remaining jamming energy after multichannel cancelling of the motion modulation jamming technique are investigated one by one from the passive and active aspects. Chapter 4 studies the compound jamming techniques based on the motion modulation jamming. Considering the practical application, to overcome the limitation that the output of the motion modulation jamming is restricted by the jammer position, two modified frequency shift jamming types in range and the Doppler frequency modulation jamming method in azimuth are proposed, which enriches the output of the motion modulation jamming. When the jammer transmits and receives signal simultaneously, the signals from the transmitter and receiver antennas need to be well isolated; and when the receiver antenna and the transmitter antenna are time-shared, the jamming signal will be delayed for a long time. For this problem, the intermittent sampling repeater jamming methods against SAR in range and in azimuth are proposed. The intermittent sampling jamming can provide a solution to the antenna difficulty, and also can be used as an independent jamming principle, which will further enrich the motion modulation jamming effects in two dimensions. Finally, an implement scheme of the motion modulation jamming technique against SAR-GMTI is provided based on Digital Radio Frequency Modulation (DRFM), which can associate with complex frequency shift jamming, the complex Doppler frequency modulation jamming and the intermittent sampling repeater jamming techniques.Chapter 5 summarizes the research work and main innovations, and discusses the future work to be researched.After all, the basic idea of the motion modulation jamming technique against SAR-GMTI is to add the phase of the stationary echo by certain phase increment values in azimuth direction for all the pulses received by the jammer. The phase increment values can represent the Doppler frequency modulation of the false moving target. The motion modulation technique is effective, dual functional, sound and feasible in practice, which has four prominent advantages. Firstly the motion modulation jamming signal can be processed coherently in range and partially coherently in azimuth, which can make up for the jamming inferiority in processing gains. Secondly the motion modulation jamming allows for the false target motion characteristics, and can protect the stationary and moving targets simultaneously. Thirdly the motion modulation jamming has weak dependency on reconnaissance systems, especially when there are no strict requirements for the false target motion parameters. Fourthly the motion modulation jamming can be implemented by small-volume, low-cost, flexible and controllable DRFM repeater. Along with the complex frequency shift jamming in range, complex Doppler frequency modulation jamming in azimuth, and intermittent sampling repeater jamming methods, the motion modulation jamming effect will be complex and various. The SAR-GMTI motion modulation jamming system constructed in this dissertation, not only enriches the electronic countermeasure theory, but most promisingly improves the survivability of important ground military moving targets against SAR-GMTI, which has an important meaning in national defense.