Time-frequency distribution of multichannel SAR-data for autofocusing of moving targets

The detection, motion parameter estimation and imaging of moving targets cause serious problems for conventional SAR systems with a single antenna. This is due to the fact that there exists the motion induced spread of the clutter spectrum and the ambiguity between the cross motion and azimuth position respectively the forward velocity and any radial acceleration. In this context time-frequency distributions are proposed which are able to analyse the behaviour of the Doppler history of different point scatterer. Using a multi-channel SAR-system equipped with antennas or subapertures in along track direction the collected data provide additional direction dependent information on target motion. The paper investigates the application of a multi-channel time-frequency distribution for estimating the target motion parameters even in the case of not pointlike reflection characteristics. The result can be used to produce a better focused image (ISAR) and correct the troublesome azimuthal displacement. The proposed algorithm is investigated by real SAR-data application.