Comparison of quadratic time-frequency methods applied to ISAR imaging of aircraft

Time-frequency analysis is useful for inverse synthetic aperture radar (ISAR) imaging of aircraft with general motion. For applications of ISAR images, quantifiable performance is preferrable. Such performance can be described in terms of effective resolution and dynamic range of an image, quantities that can be obtained from inpulse responses. The problem with this approach is that time-frequency ISAR impulse responses are signal dependent. Based on two representative test signals, four Cohen's class time-frequency methods are compared. The comparison uses estimated resolution and dynamic range from selected azimuth impulse responses. It is found that the adaptive optimal kernel estimator is best of the four tested. This method is less signal dependent than the other methods, and have reasonable dynamic range for radar imaging.