Airborne Multi-channel Radar Forward Looking Imaging And Sidelobe Suppression Method

Airborne radar forward-looking imaging has important applications in the fields of autonomous landing,autonomous navigation,and forward-looking reconnaissance and guided.However,due to the limitations of the imaging mechanism,traditional monostatic synthetic aperture radar(SAR)or Doppler beam sharpening(DBS)technologies have forward-looking imaging blind spots.By utilizing the range history differences between multiple channels and the target,multi-channel radar can eliminate the Doppler symmetry ambiguity in conventional single channel forward looking SAR imaging.Therefore,it has the potential of forward-looking imaging and has gradually become a research hotspot in recent years.It is of great research significance to exploit the advantages of multichannel resources,design a reasonable forward-looking imaging scheme,and suppress imaging sidelobes to further improve imaging effects.Focusing on airborne multi-channel radar forward-looking imaging and sidelobe suppression,this thesis investigates multi-channel radar echo modeling,forward-looking imaging scheme and sidelobe suppression methods,the main contents are as follows:1.The multi-channel radar forward-looking imaging echo model is established,the analytic expression of the echo is derived,the echo law is analyzed,the causes of leftright ambiguity in single-channel imaging and the mechanism of left-right ambiguity resolution in multi-channel imaging are revealed,which lays the theoretical foundation for the subsequent imaging scheme and sidelobe suppression.2.The multi-channel radar real aperture imaging and synthetic aperture scheme is studied,and the azimuthal resolution under the two imaging schemes is compared and analyzed.A hybrid real-aperture/synthetic-aperture forward-looking imaging scheme is proposed by fusing the single-channel synthetic-aperture imaging results with the multichannel azimuthal real-aperture imaging results,which efficiently realizes ambiguity-free multi-channel radar forward-looking imaging.3.The multi-channel forward-looking SAR sidelobe suppression method based on coherence factor is studied,the problems of existing coherence factor sidelobe suppression methods are analyzed and simulated,and the multi-channel forward-looking SAR sidelobe suppression method based on spatially smoothed coherence factor is proposed.Based on the idea of subarray smoothing,this method calculates the coherence between echo signals by creating partially overlapping subarrays of the same length,which can achieve a good balance between sidelobe suppression and background contour preservation.It is verified by MATLAB simulation tool that the proposed method can effectively implement airborne multi-channel radar forward-looking imaging and can effectively suppress the influence of the side lobes.