Jamming Technique For Countering LFM Pulse Compression Radar Based On Digital Radio Frequency Memory

Advanced radar systems generally employ various techniques of electronic counter-countermeasures (ECCM). Particularly by utilizing coherent characteristics of intra-pulse or interpulses, they can achieve coherent processing gain,and obviously decrease the efficiency of electronic jamming which signal waveforms are mismatched to a victim radar's transmitted waveform. These radars present significant challenges to the research on techniques of electronic countermeasures (ECM). The advent of Digital Radio Frequency Memory (DRFM) and the growing application of DRFM to electronic warfare are providing a powerful means for effective jamming to the advanced radar system, which is used to sample, store and play back intercepted radar signals with high fidelity.On the basis of both domestic and foreign advanced ECM technique and its developing trend, this thesis has studied intensively some novel jamming techniques on linear frequency modulated (LFM) pulse compression (PC) radar.Firstly, the operational principle, basic structure, the developmental history and current and future trend in other countries of DRFM are introduced systematically, together with some successful applications appearing in the literature. Undesired spurs produced by the digitizing process undergone within DRFM are theoretically analyzed, and spurs reduction techniques and methods are discussed. Main influential factors such as local oscillator and sampling clock and quantification levels for the coherency of the replica signals in DRFM are analyzed too. The operational principle and implementation of an integrated deceptive jammer based on DRFM are studied in detail.Then, the ECM and ECCM of frequency-shifting to LFM PC radar are discussed in detail, and a signature of frequency-shifting jamming is theoretically analyzed. The signature can be utilized by radar for anti frequency-shifting jamming, on the other hand, it can be utilized to direct or control the use of frequency-shifting jamming more effectively. In order to conceal the signature by all means, some reformative technologies of frequency-shifting jamming are studied too, which can make radar obtain a train of false targets or cover-pulse false targets.A novel technique of interrupted-sampling and repeater jamming based on DRFM is proposed and studied in detail, its principle and jamming effect to LFM PC radar is analyzed in theory, and its physical explanation and some significative conclusions are given out; the effect and influence of key parameters is discussed emphatically. The conclusions show: the technique of interrupted-sampling and repeater jamming is different from the former deception ECM, which gives out error information such as range deception or velocity deception or angle deception by manipulative modulation to victim radar. The technique of interrupted-sampling and repeater jamming utilizes coherent characteristics of intra-pulse to attack LFM PC radar, and makes radar obtain a train of lifelike false targets without any identified features. In a word, the technique of interrupted-sampling and repeater jamming is better than the former deception ECM.On the basis of studying on interrupted-sampling and repeater jamming, a new jamming technology of interrupted-sampling and circular-repeater jamming is presented, including two algorithms such as repetitive repeater and one by one circular repeater. The jamming effect of both algorithms is analyzed, and the effect and influence of key parameters is discussed emphatically. Both jamming algorithms can make LFM PC radar obtain numerous lifelike false targets, and the number and amplitude and position of these false targets can be adjusted or controlled by way of changing some parameters of jammer.Finally, the design and implementation of interrupted-sampling and repeater jammer based on DRFM is introduced.The results of this thesis are beneficial not only to design coherent jammer, but also to develop the technology of jamming theory for attacking LFM PC radar.