Research On Multiple-element Retrodirective Cross-eye Jamming

Cross-eye jamming attempts to protect a military platform against the approaching active radar seekers by transmitting two jamming signals with equal amplitude and 180°phase difference due to the induced angular error into monopulse radar.Despite the fact that cross-eye jamming was first mentioned in 1958,it has remained of interest to the electronic warfare community,due to the fact that cross-eye jamming appears to be the most effective jamming technique against the monopulse radar.In recent years,many theoretical researches and experimentations on cross-eye jamming have been done at home and abroad.However,there are still huge challenge and practical limitations for the practical application of the traditional cross-eye jamming,such as the strict tolerance requirements and the high jammer-to-signal ratio(JSR).This dissertation focuses on the enhanced application of traditional cross-eye jamming system by providing more degrees of freedom.Multiple-element retrodirective cross-eye jamming(MRCJ)based on onedimension/two–dimension retrodirective antenna array has been proposed and analyzed.According to the comparison of jamming performance between the traditional cross-eye jamming and MRCJ,some reasonable advices are provided.Chapter 1 presents the background and significance of this dissertation,introduces the research status of the cross-eye jamming,and finally points out the work of this dissertation.Chapter 2 introduces the jamming principle and discusses some important issues associated with the traditional two-element cross-eye jamming.This chapter firstly explains the jamming principle of the traditional cross-eye jamming from the perspective of phase-front distortion,then analyzes the reason why the retrodirective antenna implementation appears to the only way to make cross-eye jammer practical,and summarizes the research results and the general conclusions for two-element retrodirective cross-eye jamming.The practical limitations of two-element cross-eye jamming are analyzed and the fact that increasing degrees of freedom of cross-eye jamming system can enhance its efficiency in practical application is indicated finally.Chapter 3 proposes multiple-element linear retrodirective cross-eye jamming(LMRCJ)based on one-dimension linear retrodirective antenna array,and gives its mathematically rigorous derivation.This chapter sets two different jamming geometries,then gives the expressions of monopulse ratio,monopulse indicated angle and cross-eye gain of L-MRCJ.Studies show that L-MRCJ can obtain better jamming performance comparing with two-element retrodirective cross-eye jamming due to the advantage on increasing degree of freedom and self-phase modulation.Chapter 4 analyzes the tolerance requirements on L-MRCJ.This chapter defines the settling angle and angle factor which characterizes the performance of L-MRCJ system,gives the way to compute the parameter tolerances associated with L-MRCJ.Furthermore,the effects of jammer range,base length ratio between jammer loops and loop differences on the tolerance requirements are analyzed,and reasonable advice for overcoming the above effects are presented.Simulation results demonstrate that the tolerance requirements on L-MRCJ system are much looser than those on two-element retrodirective crosseye jamming system.Chapter 5 investigates the performance of L-MRCJ in the presence of platform skin return.After giving the signal model of platform skin return,this chapter presents the total sum-and difference-channel returns and derives the total monopulse ratio and total cross-eye gain.Considering that the total cross-eye gain is a random variable determined by the variable phase of platform skin return rather than a single value,the cumulative distribution function of total cross-eye gain and the statistical values of total cross-eye gain are derived under the assumption that the phase of platform skin return is uniformly distributed over all angles.The relationships between the JSR and the statistical values of total cross-eye gain are derived by defining the jammer-to-signal ratio.Investigations show that L-MRCJ can achieve the same performance to two-element retrodirective crosseye jamming with lower JSR.Chapter 6 proposes multiple-element circular retrodirective cross-eye jamming(CMRCJ),and gives its mathematically rigorous derivation.Aiming at the problem that the performance of L-MRCJ and C-MRCJ vary rapidly when the platform rotates in practical operations,this chapter further proposes improved C-MRCJ which changes modulation directions adaptively according to the information of direction of incident wave of monopulse radar.Studies show that improved C-MRCJ can achieve continuous and stable jamming performance with the optimal array configuration,and improved C-MRCJ can break the limitations of keeping the platform motionless associated with traditional cross-eye jamming.Chapter 7 makes a summery of this dissertation,outlines some new conclusions on cross-eye jamming,and points out several open problems in the future research.