Research On Techniques Of Clutter Suppression With Satellite-bone SAR Of Space Arrangement

Synthetic aperture radar(SAR)is a new all-weather and space-based radar system after World War II.At present,the main space borne SAR system consists of several satellite radars in a certain space configuration.Compared with the conventional SAR system,the on-board SAR system has the advantages of high spatial freedom and low system complexity,and has a wide range of applications.In this paper,the clutter suppression technique of space borne SAR system is studied.After establishing the model of SAR target and clutter echo signal,the spectrum characteristics of moving targets and clutter are studied,On this basis,the algorithm of nonstationary clutter suppression and the clutter suppression technique in the "seemingly dry accumulation interval"(long CPI)model are studied.The main work of this paper is as follows:(1)the echo signal model and moving target model of target and clutter in space borne SAR are studied.The effects of target motion on range migration,Doppler frequency and Doppler frequency are discussed.The generation mechanism of clutter and the source of clutter in echo signal are analyzed.The probability density of clutter with different distributions is discussed.The conclusion that K distribution clutter can effectively simulate other kinds of distributed clutter is proposed,and the K distribution clutter is generated by using spherically invariant random process method to suppress the algorithm.(2)space time adaptive processing(STAP)algorithms and dimension reduction methods for space borne SAR systems are studied in the context of non-stationary clutter Firstly,the space-time characteristics of clutter are analyzed,and the effectiveness of conventional STAP algorithm for suppressing non-stationary clutter is studied.The spectral characteristics of distance to non-stationary clutter and the influence on the echo signal are studied.To find the spectrum characteristics and pitch of nonstationary clutter to the relevant information,according to the characteristics of satellite array configuration,will be extended to the conventional STAP algorithm to empty(azimuth)-space-time(elevation)of the 3D STAP algorithm,using the pitch dimension information increased echo and clutter,to achieve suppression of non-stationary clutter.The simulation results show that the 3D STAP algorithm can suppress the non-stationary clutter in the range.The local joint processing method(JDL)and the pre-and post-space adaptive processing method(3DT-STAP)can reduce the computational complexity and the performance loss of the algorithm.(3)The spectrum of the echo signals of long CPI and short CPI SAR systems is studied,and the spectrum characteristics of clutter are studied.It is found that the conventional STAP technology cannot continue to be applicable.The whole space-time signal projection in Doppler frequency domain subspace,according to the independent clutter subspace of space-time signal dimension,local STAP processing in the sub space inside,will handle all the subspace results using stationary target squint imaging algorithm for coherent accumulation,simulation experiment local STAP treatment and the coherent accumulation of the validity of the results,analysis of the size of CPI and the effect of the length of the satellite baseline processing results of STAP.