Research On Missile-borne Forward Squint Synthetic Aperture Radar Imaging Technology

The new generation of precision guided weapons is demanded not only to identifyand destroy the high-value military targets quickly and accurately, but also to work inall-weather, all-time and long-range conditions. Therefore, the pattern that syntheticaperture radar is used in missile platform for two-dimensional imaging guidance hasreceived increasing attention. This paper is focus on the forward squint imagingtechnique of the cruise missile when it is cruising, including squint echo data simulation,forward squint imaging technique and squint motion compensation technique based onthe INS measured values.Firstly, based on the chirp signal and the pulse compression, the principle of SAR isintroduced from the perspective of range resolution and azimuth resolution. The squintgeometry mode and echo signal mode are given. The two-dimensional coupling of echosignal is analysed and the secondaty range compression is needed in order to decoupling.The range migration affects imaging significantly in squint mode. So the character ofrange cell migration of squint mode is studied. High order approximation of the distanceequation is used to satisfy imaging requirements of squint mode.Secondly, the squint mode SAR echo signal simulation is studied and simulationmethod is proposed. The geometry mode of squint mode SAR echo signal simulation isestablished and calculation expressions of several key parameters for simulation areobtained according to detailedly analysis and dedution.Thirdly, the imaging algorithm of squint mode SAR is studied. The echo signalspectrum of forward squint mode SAR is analysed thoroughly. The change law ofcoupling phase and squint angle and carrier frequency is summarized. An advancedrange-doppler algorithm of forward squint stripmap mode SAR is proposed. By thesecondary range compression, the imaging focus effect is improved. By compensatingthe cubic phase term, the problem of range compression distorted sidelobe is improved.By compensating the azimuth parallel phase term, the shift of image location in azimuthis solved. An improved method of range migration correction is presented. Frequencydomain correction is used instead of the traditional interpolation to improve thecalculation efficiency. The algorithm flow is given and some simulations are shown to verify the effectiveness of the algorithm.Lastly, the effect of translational motion error on imaging during missile cruising isstudied. The translational motion error is divided into errors in ground speed directionand line of sight direction and the modes of motion errors in two direction areestablished. The phase error and envelop error caused by motion error are discussed.Based on the INS measured values, the method of motion compesation is proposed.Combined with advanced range-doppler algorithm, the simulations verify theeffectiveness of the method of motion compesation.