Double Base Squint Synthetic Aperture Radar Imaging Technology Research

Bistatic Synthetic Aperture Radar is a new concept in radar community. Due to its bistatic characteristic, bistatic SAR has many advantages, such as abundant field information, remote detecting distance, high security, and fine anti-jamming performance, etc., in comparison with the monostatic case. Because of these characteristics, it has become a significant imaging technique in both military and civil fields and is receiving considerable attention recently. Moreover, squint mode can extend the bistatic SAR's working flexibility and obtain more plenty information. Focusing on the imaging theories of bistatic squint mode SAR, the main work of this thesis is shown as follows:1. The geometry model and signal model of the bistatic translational invariant squint SAR (BTIS-SAR) are presented. In specific, two methods, the Loffeld model and the method of series reverse, are used to deduce the two dimensional (2D) spectrum of the BTIS-SAR. The difference and consistency of these two methods are also given through theoretical analysis and numerical simulation.2. The Doppler properties of the BTIS-SAR are derived; the influences of the quadratic approximation on the Doppler properties are presented. Moreover, the relationships between the Doppler parameters and the bistatic squint angles are analyzed.3. By analyzing the variance of the synthetic aperture length resulted from the bistatic characteristic and the squint mode, the resolution properties of BTIS-SAR are presented. The influences of the bistatic squint angles on the resolution properties are given as well.4. An imaging algorithm named BTIS-RMA (Bistatic Translational Invariant Squint Range Migration Algorithm) is proposed based on the Loffeld model for bistatic SAR 2D spectrum. The essential step of Stolt mapping is analyzed in detail. The numerical simulation results show that, the quality of images focused by the BTIS-RMA is much better than that of the SIM (Squint Imaging Mode) algorithm in the case of large squint angles. In addition, the algorithm is employed to focus a real bistatic SAR data set successfully.5. To apply RMA to real SAR data set, a method based on the four order Doppler parameters is proposed to get the accurate platform's motion parameters.