| The major problem in the research field for hypersonic weapons guidance radaris the detection, reselution and recognition of stationary or slow moving target in theground or the sea. High resolution imaging technique is the effective way to solve thisproblem. Because the instantaneous bandwidth of the missile phased array radar islimited, synthetic broadband technoligy needs to be used to meet high resolutionimaging requirements, the key issues in which are how to improve the data rate,anti-interference ability, imaging quality and two-dimensional resolution ability forsynthesis broadband high resolution imaging system. Novel scheme of ahigh-pulse-repetition-frequency (HPRF) random-order stepped frequency radar withsingal model and range-Doppler two dimensional signal processing and new methodof side-lobe suppression for high resolution range imaging are presented for the aboveapplication requirements. Theoretical analysis and simulation results show that it isfeasibility to realize the high data rate for range-Doppler two dimensional resolutionand high resolution range profile for HPRF random-order stepped frequency radarsignal processing.In this paper, the mainly research work includes:(1) Signal processing method for two-dimensional resolution for HPRFrandom-order stepped frequency radarDemand analysis shows that it is necessity and feasibility to use HPRFrandom-order stepped frequency system for hypersonic weapons guidance radar.Compared to low-pulse-repetition-frequency stepped frequency radar, this new radaris superiority in the aspects of data rate, anti-interference ability, andtwo-dimensional resolution ability and so on. The signal models of HPRFrandom-order stepped frequency radar, IQ quadrature sampling, motioncompensation, pulse Doppler processing, pulse compression and range profilesynthesis have been constructed by theoretical analysis and mathematical deduction.Simulation results show the two-dimensional resolution for HPRF random-orderstepped frequency radar.(2) New method of side-lobe suppression for high resolution range imagingThe range side-lobe features are analysed for high resolution range profile forHPRF random-order stepped frequency radar and the importance of the side-lobe suppression is pointed out. The conventional side-lobe suppression method based onfrequency weighting has been analysed and there may be some problems such as highcomplexity of on-line computation and ill-condition problem such as irreversiblematrix. New methods of optimal frequency weighting vector are designed for thepurpose of minimum disc energy after time integral for HPRF random-order steppedfrequency radar. The methods avoid ill-condition problem such as irreversible matrixand the computation for optimal frequency weighting vector is translated into off-linecomputation. Considering the limitation of the missile storage capacity, another newside-lobe suppression method based on subprime weighting is presented, which canboth significantly reduce the computation cost (offline) and the storage cost. Besides,the methods needn’t design different weighting vectors according to the differentrange distinguish units, don’t exist ill-condition problem such as irreversible matrix,can translate the on-line obtaining for optimal frequency weighting vector intooff-line, and can also exchange the less side-lobe suppression loss for thesignificantly reduced storage cost.(3) Performance evaluation for side-lobe suppression algorithmThe side-lobe suppression performance for side-lobe suppression methodspresented in this paper is qualitatively and quantitatively analysed, compared andevaluated by experimental study, which contains point target range response functionand extended target range response function, the analysis of the effection of differentfrequency hopping choice for side-lobe suppression performance and the relationshipbetween the frequency hopping design and optimal frequency weighting vector.Experimental results have verified the correctness and effectiveness for the side-lobesuppression methods presented in this paper. |
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