A Study Of Forward Looking Real-aperture Imaging Method For Missile-borne Phased-array High Pulse-repetition Frequency Radar

The high-speed missile guidance radar detects stationary andslow-moving targets in ground or sea clutter background by using imagingtechnology. The search range of guidance radar is generally the directionin front of the flight area, and the forward-looking real-aperture imagingand motion compensation are an important issue which needs to be solvedin guidance radar. Because of the instantaneous bandwidth limitations ofthe phased array radar, wideband phased-array radar synthesizesbandwidth by using pulse step frequency technology. In order to improvedata rates, reduce imaging accumulated time and improve the accuracy ofmotion compensation, it needs to adopt the technology of highpulse-repetition frequency. Therefore, it is of great significance to carryout high pulse-repetition frequency synthetic wideband forward-lookingreal-aperture imaging method of high speed missile guidance radar.According to missile-borne stepped-frequency widebandphased-array radar with application of target detection in ground or sea clutter background of real-aperture forward looking imaging, this paperpresents the forward-looking real aperture super-resolution imagingmethod and its technical ways to realize the functions. The innovationsresearch work in this paper mainly includes:1. A detailed analysis of phased array radar antenna pattern functionis carried out. The inseparability of antenna pattern in pitch-azimuth planeand time(space)-varying during beam scanning is pointed out. Nonlineartransform based on angle coordinates and the azimuth non-uniformsampling of pattern function separation method is proposed. In modifiedpitch-azimuth coordinate system, the separation of the pattern function canprovide favorable conditions for forward-looking super-resolution imagingby using least square criterion and multi-channel deconvolution so that theimaging problem can be transformed into a simple linear least squarecriterion problem and linear deconvolution problem.2. Mono-pulse sum channels and difference channels signal modelsof phased array high pulse-repetition frequency synthetic wideband radarand various mathematical models in the signal processing of forward-looking real-aperture imaging are established. A motioncompensation method for forward-looking real aperture imaging process isstudied and proposed. The importance of high-repetition-frequencytechnology to improve the accuracy of motion compensation and theforward-looking image quality is analysised and pointed out;3. Novel method of two-dimensional real-aperture range-azimuthimaging and motion compensation is presented for missile-bornestepped-frequency wideband phased-array radar with application of targetdetection in ground or sea clutter background by using non-uniformscanning of beam in azimuth direction and least square criterion.Compared with the traditional methods of real-aperture forward lookingimaging, the method has advantages of adaptation to inseparability ofantenna pattern in pitch-azimuth plane, adaption to time-varying antennapattern during beam scanning, no requirement for cutting of antennapattern, low computation complexity, suitability of pipeline parallelprocessing during scanning and higher imaging resolution.4. The sum and difference dual-channel deconvolution forward-looking imaging method of traditional monopulse is promoted tophased array stepped frequency synthesis wideband guided radar andhigh-speed guided application. The pattern function fitting, orientation tonon-uniform sampling and dual-channel deconvolution are presented forforward-looking real aperture super-resolution imaging method. Thefeatures of the method are: the main process of signal processing isFourier transform, and it facilitates the use of dedicated signal processingchips like FFT (Fast Fourier Transform). But compared with the leastsquare criterion, it has a slight decline in resolution performance.Theoretical analysis and simulation results show that the highrepetition rate and the appropriate motion compensation can effectivelyovercome the impact of the missile and target relative motion of theforward-looking real-aperture imaging; Azimuth resolution of far less thanbeam-width is available for super-resolution method of linear least squarecriterion and multi-channel deconvolution processing to achievingforward-looking real-aperture imaging.