Micro-doppler Analysis of Rotating Targets in Dual-channel Bistatic SAR

摘要

The micro-motions of structures in a target, such as the rotor of a helicopter, the scanning antenna of a ship, the vibrations of vehicle engines, may induce additional frequency modulations on the returned radar signals and generate sidebands about the center Doppler frequency of the target's body, which is known as the micro-Doppler effect. Extraction of micro-Doppler signature is very useful for target classification and recognition. In recent years, the researches of micro-Doppler extraction methods are widely discussed. However, few of them are based on bistatic SAR which has many advantages. Bistatic SAR may have a counter-stealth capability and the receivers are passive which is undetectable. Rotation is a typical micro-motion form. Most of the published researches on analysis of the rotation target did not pay enough attention to the interference of ground clutter. However, ground clutter caused by the presence of stationary targets makes the extraction of the micro-Doppler signature difficulty, which may submerge the signals of rotating targets. In this paper, based on the configuration of bistatic SAR with a dual-channel fixed receiver, a new micro-Doppler signature extraction method is used to extract the micro-Doppler features and estimate parameters of rotating targets. The received signals' expressions of rotating targets are established in the case of dual-channel fixed-receiver bistatic SAR. With displaced phase center antenna technique, the ground clutter is suppressed and the signals of rotating targets are reserved in the range-compressed data domain. Then the mathematical expressions of micro-Doppler are derived. The fractional Fourier transform is adopted to compensate for the radar Doppler shift and the Gabor transform method is utilized for extraction of micro-Doppler information caused by rotating targets and parameter estimation. Finally, The effectiveness of the proposed method is evaluated through simulations.