Bistatic ISAR Imaging and Scaling Algorithm Based on the Estimation of Bistatic Factor and Effective Rotation Velocity

For bistatic inverse synthetic aperture radar (ISAR), the most important task is to obtain high-quality and high-precision scaled bistatic ISAR images of targets, which involves two main stages: imaging process and scaling process, to improve the correctness of target recognition and classification. Without tracking and angle measurement devices, it is challenging to estimate the time-varying bistatic factor and effective rotation velocity (ERV), both of which are necessary to eliminate image distortion and two types of defocusing effects (range-defocusing effect and azimuth-defocusing effect) in imaging process and calculate the scaling factor in scaling process. In this article, an algorithm based on the estimation of bistatic factor and ERV for bistatic ISAR imaging and scaling is proposed. It can estimate the bistatic factor and ERV by using the phase coefficients of the received signals, the direction of the receiver's beam center, and the measured distance information, without tracking and angle measurement devices. After that, image distortion and range-defocusing effect can be eliminated and scaled bistatic ISAR images can be obtained. For the scaled bistatic ISAR images, if the no-azimuth-defocusing condition is not satisfied, postphase compensation should be carried out, which can eliminate the azimuth-defocusing effect to obtain the final focused and scaled bistatic ISAR images. The proposed algorithm is capable to produce high-quality and high-precise scaled bistatic ISAR images and perform well even in the presence of a low SNR condition. Simulated results validate the effectiveness and robustness of the proposed algorithm.