Airborne Bistatic Forward-looking SAR Moving Target Detection Technology

In airborne bistatic forward-looking synthetic aperture radar(SAR),transmitter and receiver are placed on different platforms,which can realize forward-looking detection for receiver,solving the Doppler ambiguity problem of mono-static SAR,with the capability of anti-disturbing and anti-detecting.So airborne bistatic forward-looking SAR is significant both in military and civilian fields.Airborne bistatic forward-looking SAR moving target detection technology is based on airborne bistatic forward-looking SAR system and the technology is designed to detect moving target from the background clutter and noise through the signal processing methods,which is the foundation of further target location and target recognition.However,there is few study on moving target detection for airborne bistatic forward-looking SAR.This paper proposes two different moving target detection methods.The main contents are as follows:1.This paper researches the echo characteristics in airborne bistatic forward-looking SAR system,establishes echo models for clutter and moving target,focusing on analyzing the range migration characteristic and Doppler characteristic,which lays the foundation for study on clutter suppression and moving target detection.2.A dual-channel moving target detection method in echo domain for airborne bistatic forward-looking SAR is proposed,which solves the problem that under translationally invariant mode,for one transmitter channel and two receiver channe ls configuration,after time shift the equivalent phase center of transmitting and receiving channel is not in the same location.This technology applies dechirp operation in azimuth phase before time shift to eliminate the effect of transmitter movement on the equivalent phase center,and then compensate constant phase for each target location in Doppler domain to remove phase deviation.While for moving target,there are still azimuth time phases after dechirp operation and a velocity phase can be constructed by time shift in azimuth,separating moving target from clutter.So the moving target can be detected from subtracting two channel images.3.A dual-channel moving target detection method in image domain for airborne bistatic forward-looking SAR is proposed,which solves the problem that under translationally variant mode,there is range history deviation between two channels for stationary clutter and the deviation varies with azimuth time and target location.Using the idea of BP algorithm,the technique compensates time delay phase caused by range history for each target location during the whole synthetic aperture time to solve the problem that the dual-channel range history deviation is hard to compensate as it is not only time-varying but also space-varying.While for moving target,there are still phases caused by target moving after time delay phase compensation,so moving target can be remained and clutter can be suppressed from subtracting two channel images.The effectiveness o f above two methods are verified by both theory analysis and simulation experiments.The experiment results demonstrate that the two methods are able to achieve airborne bistatic forward-looking SAR slow moving target detection in various situations.