Research On SAR/ISAR Imaging Algorithms For Targets With Complicated Motion

Radar imaging technique has achieved a stupendous application in the numerous domains,such as the terrain mapping,marine observation and disaster forecasting,due to its features of all-day,all-weather and remote imaging.As the mature development of the object identification technique,obtaining high quality imaging result is extremely vital.The research on the imaging algorithm for targets with complicated algorithm has become a hotspot issue.In this paper,the research on the imaging algorithm for targets with complicated algorithm is mainly divided into three parts: wide-angle imaging,maneuvering target imaging and SAR/ISAR imaging for ship targets on the sea surface.One of the measuring standards for high quality images is the resolution.Acquiring high resolution ISAR images is always at the cost of increasing the imaging time,which means to aggravate the phenomenon of migration through range cell(MTRC).Therefore,researching on the wide-angle imaging algorithm that are not influenced by MTRC has significantly practical value.In this paper,the imaging principles of the two typical wideangle imaging algorithms are introduced,which are back-projection(BP)and polar formation algorithm(PFA).Via imaging for the simulated and real-measured data,the algorithms will yield high resolution images.As always,it is a difficulty and challenge to obtain high quality imaging results for maneuvering targets.Basically,the existed imaging algorithms for maneuvering target are researched and improved from the parameterized range-instantaneous Doppler(RID)algorithm.However,these existed parameterized RID algorithms do not take timevarying amplitude into account,which may decrease the quality of the ISAR image.In this paper,a time-varying amplitude estimation method based on adaptive Gaussian window is proposed,which can accurately estimate the signal's time-varying amplitude.Moreover,the RID algorithm based on the time-varying amplitude estimation is proposed,which can alleviate the influence of MTRC and radar cross-section(RCS)varying.After imaging the simulated and real-measured data,the well-focused imaging results verity the practicability of the proposed ISAR imaging algorithm.As improving the defense consciousness of the sea safety,the research on the imaging algorithm for ship targets on the sea surface becomes extremely urgent.An appropriate solution for imaging ship targets on the sea surface is hybrid SAR/ISAR imaging.Nevertheless,the image segmentation and data extraction are always implemented by manpower in the existed hybrid SAR/ISAR imaging algorithms,which vastly consumed the manpower resource.In this paper,an automatic image segmentation and data extraction method is proposed based on the clustering algorithm.Additionally,a SAR/ISAR imaging algorithm based on the automatic image segmentation is proposed.After imaging the simulated and real-measured data,the proposed algorithm is verified to be able to yield the clear imaging results.