Bistatic Spotlight Sar Imaging Algorithm And Motion Compensation Study

Synthetic aperture radar (SAR) is a kind of imaging radar with fine resolution capability and the possibility of all day operation in all weather, which is of great importance to the modernization of national defense and national economy. Spotlight mode is one of important imaging modes of SAR, which have higher azimuth resolution than the conventional stripmap SAR. In present defense field, the demands for flexibility of radar system are higher and higher, so we develop several new radar work modes: spaceborne and airborne hybrid bistatic mode. Focusing on the imaging theories, the main content and contributions are presented as follows:1. Introduce the image formation theory of bistatic spotlight SAR and analyzes the resolution problem under the spotlight mode. Describe the theory of dechirp technic which is used in the bistatic spotlight SAR at length. Explain the practical realization procedure to eliminate the residual video phase.2. To the airborne bistatic spotlight SAR system, properly to with the Chirp Z transform(CZT) and the Polar Format Algorithm (PFA) of conventional SAR, we propose an imaging algorithm for the airborne arbitrarily bistatic SAR. We build the echo model of the airborne arbitrarily bistatic spotlight SAR, compensate the phase of echo by using the way of PFA. With the analysis of the CZT, the imaging algorithm based on CZT is described in detail. The algorithm flow and parameters during the process are also developed. This approach eliminates interpolation and reduces computational complexity. It has been validated by point.3. Improve the classical range migration algorithm (RMA), and make it fit to the SA Bi-SAR imaging. We use LBF-E and Air Phase to overcome the difficulty of resolving analytical solution for the system's stationary phase point. The bistatic-deformation and azimuth-dependent range-cell-migration terms were removed with phase multiplications performed blockwise in range–azimuth subsections. The remaining quasi-monostatic term shows the characteristic of the conventional monostatic SAR besides an additional azimuth-scaling term. For the monostatic characteristic, we prefer the range migration algorithm, since it can accurately correct the range dependence of the range–azimuth coupling, as well as the azimuth-frequency dependence. For the azimuth-scaling term, an inverse scaled Fourier transformation is performed to correct it. Finally, a simulation experiment is conducted to validate the proposed processing procedure.4. With respect to the system geometry in the presence of motion error in spotlight BI-SAR, quantitative analysis of the received data spectrum and effects on imaging result are carried out. To limit the resolution loss resulting from motion error, an effective motion compensation strategy is integrated in the imaging algorithm for narrow-coverage case.