| SAR(Synthetic Aperture Radar)has a foundation in the field of SAR applications in the SAR application.High-orbit SAR operating in space at an altitude of 36000 km,has the characteristics of short interview cycle,large beam coverage,strong battlefield survival capacity,and has a unique advantage in the field of site-to-site target detection.This thesis studies issues such as ground moving target detection,imaging and parameter estimation based on high-orbit SAR systems.The main research content is summarized as follows:1.The spatial geometric model of the high-orbit SAR is established,and the slanting model of the high-orbit SAR imaging is studied;on this basis,the echo signal model of the moving target under the high-orbit SAR system is established,and the distance from the moving target is analyzed.2.The detection and imaging methods of dual-channel high-orbit SAR ground moving targets are studied.First,the equivalent phase center compensation function in the case of “stop-and-go” not applicable is derived,and the DPCA(Displaced Phase Center Antenna)technology is used to perform clutter suppression processing on the dualchannel echo after distance compression;In the above,the generalized Keystone transform is used to complete the decoupling of the range frequency and the azimuth time,the second-order and above range migration term correction and Doppler phase compensation,and the Radon transform is used to estimate the Doppler ambiguity number for linear range walk correction,and finally pass coherent accumulation realizes the imaging of moving targets.Point target and ground scene imaging simulation experiments verify the effectiveness of the proposed method.3.Aiming at the problem of pulse repetition frequency ambiguity caused by the faster target speed in the dual-channel DPCA system,a dual-frequency dual-channel highorbit SAR moving target detection and parameter estimation method is proposed.Four high-orbit SAR echo data are obtained by transmitting two working carrier frequency signals simultaneously,and the two echoes of the same working frequency are respectively subjected to range compression,clutter cancellation and range migration correction,and Newton iteration combined with discrete frequency modulation is used.The inner transform completes the Doppler parameter estimation of the moving target,and estimates the actual target speed by searching for the intersection of two speed sets.Moving target imaging and parameter estimation experiments verify the effectiveness of the proposed method.4.Aiming at the phase entanglement problem caused by the faster target speed in the dual-channel ATI system,a method using the idea of equivalent carrier frequency to expand the maximum unambiguous detection speed range is proposed.First,by imaging and registering the two-channel echo data at each operating carrier frequency,two highorbit SAR complex images are obtained through interference processing,and then the two SAR images are conjugated and multiplied to obtain a phase without twisting the difference,and then resolve the blur-free speed.The moving target parameter estimation experiment verifies the effectiveness of the proposed method. |
