Study On Long Baseline Elevation Multi-channel High Resolution Wide Swath SAR Imaging Technology

High-Resolution Wide-Swath(HRWS)is an important requirement for Synthetic Aperture Radar(SAR)imaging.The multi-channel in elevation imaging mode can break through the minimum antenna area limit and obtain the HRWS image.Because of the short baseline length,the conventional multi-channel in elevation imaging can not obtain the results of interferometric altimetry.In order to overcome this limitation,we propose a long baseline multi-channel in elevation SAR imaging mode,which is expected to achieve HRWS imaging and interferometric altimetry through the same satellite formation.The main contents of this paper include the following aspects:1.The multi-channel in elevation SAR echo signal model with long baseline is established based on the baseline length.The increase of the baseline length will cause the problem of range envelope deviation and residual phase in the echo signal.Aiming at the problems of range envelope registration and phase compensation,the oblique distance and phase which need to be compensated are estimated and compensated in a certain way.The range envelope can still be registered when the baseline length is more than 1 km,and the false target amplitude is reduced by-15 d B.To solve the problem of unknown ground target information,the slant distance of each sampling unit can be estimated according to each sampling unit,and the final imaging result is the same as that of accurate calculation of range,which effectively solves the problem of location target position information.2.The influence of long baseline on beam separation process is analyzed.The increase of baseline length will lead to grating lobes in the final imaging results.In order to suppress the grating lobes,the traditional linear array is replaced by the combination array of mutual prime and adjacent arrays.The influence of grating lobe in linear array during beam separation is suppressed by mutual prime sampling.It is analyzed that the beam separation process combined with the combination array arrangement can more effectively suppress the grating lobe in the imaging results,and the amplitude of the grating lobe can be suppressed below-30 d B when the baseline length is 1 km,so as to eliminate the influence of the grating lobe on the imaging results.3.For long baseline multi-channel in elevation SAR system,a system design method of HRWS imaging is proposed in this paper,and corresponding parameter examples are given.The imaging resolution of the system is 1 meter,and the swath is 100 km.According to the performance of the system,the range ambiguity ratio and equivalent backscattering coefficient are analyzed in detail,and the simulation results show that the range ambiguity ratio of the system is less than-20 d B,which meets the requirements of the system design.