High Resolution Imaging Algorithms For One-Stationary Bistatic Synthetic Aperture Radar

One-Stationary Bistatic Synthetic Aperture Radar,where the transmitter or the receiver is stationary,is a special configuration of BiSAR.Compared to traditional monostatic SAR,this kind of BiSAR offers particular advantages like flexible configuration,reduced cost,forward-looking imaging ability,strong antijamming capability.In addition,it is relatively easy to be constructed and deployed,which is of great value to research.With the development of SAR imaging technology,OS BiSAR combined with moving platforms are widely used in military detection fields.But focusing azimuth-variant BiSAR data is still a great challenge for image formation algorithms,and thus most algorithms are not applicable to handle OS-BiSAR case,such as guided missiles and unmanned aerial vehicles.Their flight paths are flexible.According to their motion characteristics,their imaging modes are generally divided into two cases,such as the straight track with constant velocity and the curved trajectory with acceleration.For level flight of OS BiSAR,the results of the LRWC and inherent azimuth-variant geometric configuration produce two-dimensional(2-D)variant range cell migrations and azimuth-dependent Doppler parameters.For the curved trajectory with acceleration,spectrum aliasing and 2-D variance also exist,which leads to image quality degrades.The whole dissertation mainly contains two aspects as follows.For the OS BiSAR system along a straight track with constant velocity,an ENLCS imaging algorithm based on an equivalent analytical model is proposed First,the spatial geometry model is constructed,and the echo signal characteristics are analyzed.Especially Range offsets result from inherent configuration and LRWC are studied in detail.Following which,an equivalent analytical model is established to reveal the relationship of slant ranges.Based on this model,approximation for the azimuth-variant Doppler parameters from the azimuth distributed targets is accomplished.Finally,the equalization for Doppler phases and focusing for point targets are achieved by ENLCS.Simulation results at the end of this letter prove the effectiveness of the proposed algorithm.For the curved diving OS BiSAR system,an FENLCS imaging algorithm based on equivalent sphere model is developed.Firstly,the geometric configuration in a three dimensional coordinate system is constructed to analyze parameters,i.e,property from the altitude of platform and beam center slant range of receiver.Furthermore,the correction of accelerated velocity is performed to remove spectrum aliasing.Taking into the characteristics of high-resolution and highly squinted OS BiSAR account,a sphere model is come up with to describe the spatial variant of slant ranges and Doppler parameters after range processing.FENLCS imaging algorithm combined with this model is adopted to correct the property of the Doppler frequency modulation(FM)rate and the high-order terms of azimuth phases for the achievement of focusing in azimuth time domain.