Abstract: A method and system for processing radar return signals reflected from a vibrating target to determine the actual vibration frequency and to isolate a characteristic vibration of the vibrating target, including an oscillation signature function (OSF). A radar signal processor receives a stabilized phase history which includes frequency components, namely an FM sideband corresponding to a modulation imparted upon a reflected radar return signal by the vibrating target. The radar signal processor detects the FM sideband and determines a candidate vibration frequency. The stabilized phase history is filtered at a phase rotation based on the candidate vibration frequency to isolate the OSF and to determine the actual vibration frequency.