Focusing Bistatic SAR Data Under Complicated Motion Through Differential Phase Filtering in Variable Doppler Bands

• Main Authors: Yuxuan Miao, Junjie Wu, Zhichao Sun, Zhongyu Li, Jianyu Yang
• Format: Article
• Language: English
• Published: IEEE 2021-01-01
• Series: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
• Subjects: Azimuth dechirp; bistatic SAR; complicated motion; differential phase; Keystone transform (KT); large scene
• Online Access: https://ieeexplore.ieee.org/document/9531492/

Bistatic SAR (BiSAR) imaging is becoming more and more mature, nevertheless restricted by the significant problem of 2-D space-variation of echo signal. In practical applications, the geometry configurations and platform motion of BiSAR are often complicated, making the problem of space-variation severe and causing it hard to efficiently process BiSAR data of large imaging scene. Focusing on this problem, this article proposes a new imaging method for large scene-size imaging that can adapt to general spotlight BiSAR with complicated platform motion. This method first roughly focuses the echo data in range-Doppler domain through azimuth-dechirp and removes the residual range-azimuth coupling via Keystone transform. Then making use of the tolerance of SAR imaging to slight phase error, the full Doppler axis is down-sampled with a certain ratio to form a much smaller amount of Doppler cells called Doppler bands. Through restricting the value of the down-sampling ratio, the variance of differential phase in each Doppler band after the dechirp is controlled within a given tolerance. As a result, the differential phase can be compensated for in variable Doppler bands for a large imaging scene with high efficiency. The computational complexity of the proposed method is indicated as low as logarithmic and its effectiveness is verified through numerical simulations.