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High Resolution Imaging Algorithms For Airborne Bistatic Synthetic Aperture Radar

Posted on:2020-01-10Degree:MasterType:Thesis
Country:ChinaCandidate:A B YanFull Text:PDF
GTID:2428330572461593Subject:Information and Communication Engineering
Abstract/Summary:PDF Full Text Request
Bistatic Synthetic Aperture Radar(BiSAR)is a new type of radar,where the transmitter and receiver are located on two different platforms.Due to the separation of the transmitter and the receiver,the BiSAR can configure the geometry of platforms according to the different requirements of imaging applications.Compared with the conventional monostatic SAR systems, the increased flexibility of the bistatic SAR systems has broad application prospects because it can perform forward-looking imaging,acquire abundant information of point targets,and has low transmitting power and strong concealment.One-stationary bistatic SAR(OS BiSAR)refers to a new system of bistatic SAR with one platform moving and another fixed.Because of its simple and flexible configuration,OS BiSAR is often used to verify the imaging experiment of bistatic SAR.Due to the fact that the relative position of OS BiSAR between the transmitter and the receiver platform changes with the azimuth slow time,the signal data will be subject to the characteristic of the 2-D spatial variance of the RCM and the azimuth dependent Doppler frequency modulation factors,which will increase the imaging difficulty in the wide-swath,high-resolution and high squinted cases.Taking into account the above situations,this paper mainly focuses on the OS BiSAR imaging algorithm.And the main research contents are as follows:1 An OS BiSAR imaging algorithm based on the iso-ESBR spatial variant model is proposed to correct the 2-D spatial variant and Doppler FM factors,and remove the range-azimuth coupling.An analytical relationship of iso-equivalent-sum-of-bistatic-range(iso-ESBR)of azimuth distributed targets is derived after range cell migration correction(RCMC)which is combined by linear range walk correction(LRWC)and keystone transform(KT).Following which,a new spatial variant model is constructed to analyze the azimuth-variant property of the Doppler FM factors. Based on the spatial variant model,an improved ENLCS algorithm with new coefficients is derived to accomplish the azimuth equalization for azimuth compression.Simulation results validate the effectiveness of the proposed algorithm.Finally,the simulation results prove the effectiveness of th?proposed algorithm.2?An high-precision analytical range model is investigated to remove the 2-D residual spatial-variant RCM and range compression terms of all the targets in the imaging scene for the purpose of improving the range processing performance.First,the bulk RCMC and bulk second range correction(SRC)are carried out in frequency domain to compensate the high-order RCMs and range compression terms after the LRWC used to remove the range walk and the Doppler ambiguity of the echo data in range direction.Following which,the new analytical model is proposed to reveal the azimuth dependent characteristic of receiving range of the point targets,and to remove the azimuth dependent range offset.3?An Improved imaging algorithm based on the analytical range model is proposed to obtain better focusing for widen-swath highly squinted OS-BiSAR in this paper.First,the analytical expression of Doppler FM factors and phases is acquired according to the analytical model.And then,the influence of quadratic phase error(QPE)caused by the analytical expression is studied,and simulation evaluation and comparison are carried out to verify the high accuracy and validity of the analytical range model.After that,an extended NLCS algorithm based on this new model is proposed to enhance the performance of azimuth equalization and compression obviously in the case of wide-swath high-resolution highly squinted configuration.Finally,the simulation results prove the effectiveness of the proposed algorithm.
Keywords/Search Tags:one-stationary bistatic synthetic aperture radar(OS BiSAR), spatial variant model, analytical range model, 2-D spatial variance, wide swath, high resolution, range cell migration correction(RCMC), ENLCS algorithm
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