Research On The Three-dimensional Resolution And Sidelobe Suppression Algorithm Of Miso Circular Ground-based SAR

Circular ground-based SAR is a new ground-based SAR that introduces the airborne circular SAR mode into the ground-based platform.Compared with traditional linear ground-based SAR,it has three-dimensional imaging capability,short single data acquisition time,and timeliness of landslide monitoring.In recent years,the development of ground-based SAR systems with 3D imaging capability has become an international research hotspot.As a new ground-based SAR model,circular ground-based SAR is still in its infancy.Currently,the feasibility of using circular mode for 3D imaging has been verified internationally.But,its 3D imaging quality is still far from the imaging quality requirements of actual applications.Existing research has verified the 3D resolution capability of circular ground-based SAR with the single input single output(SISO)mechanism through simulation.However,the existing sidelobe suppression technology can't effectively solve the problem of high sidelobes in the circular ground-based SAR 3D imaging.This paper focuses on the sidelobe suppression problem of circular ground-based SAR in the 3D imaging process.We proposes a circular ground-based SAR system with the multiple input single output(MISO)mechanism.From its geometry,signal model,spectrum,point spread function(PSF)and sidelobe suppression,a systematic study has been carried out.The main research content and innovative results are as follows:(1)The geometry and signal model of MISO circular ground-based SAR is established.Based on this model,a 3D imaging algorithm suitable for MISO circular ground-based SAR is introduced.The 3D imaging performance of SISO mechanism and MISO mechanism are compared.Their 3D spectrum support domain are also analyzed in depth.It provides a basis for finding out the reason that SISO circular ground-based SAR has high sidelobe in the 3D imaging.(2)From the spectrum analysis,the point spread function and resolution of MISO circular ground-based SAR are derived.On this basis,the 3D resolution,sidelobe,and space-variant property of circular ground-based SAR with SISO mechanism and MISO mechanism are separately analyzed.The sidelobe suppression capability of MISO circular ground-based SAR is also analyzed.(3)Aiming at the high sidelobe problem of SISO circular ground-based SAR in the azimuth-vertical plane,a sidelobe suppression method for MISO circular ground-based SAR is proposed.It is a spectrum sparse sidelobe suppression method based on phase change diagram analysis,which broadens the frequency spectrum by way of sparse spectrum distribution to suppress high sidelobes.This method uses phase change diagram to find the optimal spectrum distribution under the condition of a given antenna number and bandwidth-frequency ratio.The MISO circular ground-based SAR based on this optimal spectrum distribution has the best sidelobe.Finally,according to the geometry between the array antenna distribution and the spectrum distribution,the corresponding optimal sparse array antenna distribution can be found.(4)Using the MISO circular ground-based SAR model with the optimal sparse array antenna distribution and the corresponding 3D imaging algorithm,the 3D SAR image of point target and lattice targets are simulated.Comparing with the 3D imaging results of existing circular ground-based SAR,it verifies that the proposed model and method is effective.