Study On Multichannel Synthetic Aperture Radar Ground Moving Target Indication And Wide Swath Imaging Technology

Synthetic Aperture Radar(SAR)system plays an important role in both military and civil fields with the ability to provide high resolution image all-time and all-weather.Equipped with a multichannel receiving antenna,the multichannel SAR ground moving target indication(GMTI)system effectively reduces the minimum detectable velocity(MDV)of ground slowly moving target by employing space-time adaptive processing(STAP)technique to suppress ground clutter.Therefore,SAR-STAP clutter suppression technology has become one of the key technologies in GMTI.Furthermore,the multichannel SAR system can also obtain high resolution and wide swath image simultaneously by removing the Doppler ambiguity caused by low pulse repetition rate(PRF)through spatial signal processing.This thesis focuses on the research of multichannel SAR ground moving target indication and wide swath imaging technology based on ambiguity removal in Doppler domain.The main contents are as follows:1 The multichannel SAR-STAP clutter suppression technologies are studied.The model of echo signal collected by airborne multichannel SAR system is established.The difference of Doppler between moving target and stationary target among the echo signal is analyzed in detail.Then,classical multichannel SAR clutter suppression algorithms including clutter suppression interferometry(CSI)and image domain synthetic aperture radar space-time adaptive processing(SAR-STAP)are studied,with the performance verified by experimental results.2 The multichannel SAR moving target detection technology in non-gaussian environment is studied.The performance loss of traditional SAR-STAP algorithm in practical non-Gaussian clutter environment is investigated.The Alpha stable distribution is introduced to replace Gaussian distribution for clutter suppression in non-Gaussian environment.Based on that,a new SAR-STAP clutter suppression algorithm is proposed,which employs the minimum fractional low order moment distortionless(FrMVDR)criterion to generate adaptive weight vector.As is verified by simulation as well as experimental results,detection performance of the new algorithm obviously outperforms that of the traditional SAR-STAP algorithm in the non-Gaussian clutter environment.3 The multichannel SAR wide swath imaging technology based on ambiguity removal in Doppler domain is studied.Firstly,both the nonadaptive and adaptive Doppler ambiguity removal methods,based on filter banks and adaptive digital beamformer,are studied and verified by simulation and experiment results.Moreover,considering the velocity of platform is unstable in practical,the full aperture unambiguity data cannot be directly reconstructed at one time when the coherent processing interval(CPI)is relatively long.To remedy this,a new algorithm based on sub-aperture processing is proposed to process unambiguity data collected in long CPI.In this algorithm,the full aperture data is firstly divided into multiple sub-apertures,which will undergo ambiguity resolving independently.The processed sub-apertures data are then combined to generate the full aperture data with Doppler ambiguity removed,which is used in the following SAR imaging procedure to obtain high resolution wide swath SAR image.The performance of this algorithm is also verified by experimental results.