Research Of The Airborne Side Looking Bistatic Synthetic Aperture Radar Imaging Algorithms

In recent years, Synthetic Aperture Radar(SAR) has been a hotspot in radar image field.Due to the fact that Bistatic Synthetic Aperture Radar(Bi-SAR) system transmitter and receiver were installed on different platforms, Bi-SAR has different spatial location and velocity, which makes it could obtain more additional information in scattering coefficient of target about the target. So it has great value in military affairs and national economy, and could be used in many fields.The separate transmitter and receiver makes Bi-SAR range equation is the sum of them,which has a double square-root form,therefore,it is more complicated than monostatic SAR.What is more, different configuration's Bi-SAR has the different imaging algorithm, and how to solve the double square-root range equation is the key point for the Bi-SAR. At last,we study the imaging algorithms for Bi-SAR. The side Bi-SAR has a large Doppler bandwidth,and has many similar characteristics with monostatic SAR, therefore, monostatic SAR imaging algorithm can be applied to side looking Bi-SAR by some improvements. This thesis studied side looking Bi-SAR of Range-doppler algorithm and Chirp scaling (CS) algorithm,the main contents are as follows:Firstly, this thesis built the model geometry and echo under the side looking. After that,the resolution characteristics and the impact of Bi-SAR imaging quality range migration phenomenon and swath selection were discussed.Secondly,in order to obtain the point target reference spectrum of Bi-SAR, we make the Bi-SAR equivalent to monostatic SAR. That is to say, the double square-root range equation becomes a single root,obtaining two dimensional spectrum of equivalent monostatic SAR.After that, we obtain two dimensional spectrum of LBF by Taylor and POSP, and analyzed the two methods applicable conditions in the side looking mode at the same time.Finally, we studied the Bi-SAR imaging algorithm in side looking mode. Range-Doppler(R-D) algorithm is the most simple and classic SAR imaging signal processing algorithms,nevertheless, the algorithm usually requires interpolation operation. Based on LBF two dimensional spectrums, we proposed the novel R-D algorithm. Instead of the interpolation,the modified R-D algorithm range migration was corrected by phase correction, which verifies its effectiveness by data simulation. After that, combining equivalent monostatic's two dimensional spectrum with the CS algorithm,the Bi-SAR CS algorithm was presented,which the azimuth Fourier transform can be solved directly. Finally through the analysis of calculated amount and the simulation results,we could find that the proposed algorithm is suitable for Bi-SAR imaging, and verified the validity of the novel algorithm.