Research On Bistatic Forward-Looking SAR Clutter Suppression And Moving Target Detection Methods

Breaking through the limit of traditional monostatic synthetic aperture radar(SAR),bistatic forward-looking SAR(BFSAR)can work full-time and all-weather to provide images with high resolution of the forward-looking terrain of the receiver,by separating the transmitter and the receiver in two different platforms.Additionally,the receiver also has benefits such as electromagnetic silence,high anti-interference and so on.Therefore,BFSAR is practically valuable and promising in many fields,especially air-to-surface attacks.BFSAR clutter suppression and moving target detection aim to distinguish and detect ground moving target(GMT)as well as suppress clutter in forward-looking areas,by utilizing discrepancies between GMT and background clutter echo in space-time-frequency and image domains,via the techniques such as multichannel cancellation and so on.Clutter suppression and GMT detection are important roles in BFSAR-ground moving target indication(GMTI).This dissertation focuses on the theoretical research and the method verification in clutter modeling,clutter characteristic analyzing,clutter suppression and GMT detection involved in BFSAR-GMTI.The main contents are divided into following four parts:1.A BFSAR geometric modeling method based on the non-standard elliptical coordinates calculation is researached.The space-time clutter model in BFSAR is derived and the non-stationary characteristic of BFSAR clutter is analyzed,which builds a theoretical foundation for the research of clutter suppression and GMT detection methods.2.A BFSAR clutter suppression method based on cascading cancellation is proposed.Through the adaptive cancellation on range bins and the secondary cancellation on images,the problem of insufficient clutter suppression caused by the separation of the receiver and the transmitter can be solved.With the cascading cancellation,clutter in forward-looking terrain can be jointly suppressed in echo domain-image domain.3.A BFSAR clutter suppression method based on matched space-time filtering is proposed.Through the space-time filter optimally modelling and acquiring filter weight via optimazition method,the influence of strong non-stationarity of clutter can be eliminated,and the goal of effective BFSAR clutter suppression in space-time domain is realized,which guarantees well performance in GMT detection.4.GMT detection methods based on the two-dimensional deramp processing and Ksystone-based delay-correlation transform are proposed for BFSAR system.The problems of GMT energy accumulation and Doppler parameter estimation under a low signal-to-noise ratio(SNR)condition can be solved by thses methods,making achievements on effective GMT detection and parameter estimation.On the basis of theoretical research,I assisted the research group in finishing several airborne flight verification tests,and the first airborne BFSAR-GMTI experiment in the world is realized.The methods mentioned above have been verified in this dissertation by theoretical analysis,numerical simulation and experimental data processing.The results illustrate that these proposed methods can effectively suppress strong non-stationary BFSAR clutter,detect GMT from the received echo,estimate Doppler parameters of GMT,and then realize BFSAR-GMTI.