Extraction of Instantaneous Frequencies from Time-Varying Bispectrum Estimates of Coherent Radar Echo Responses for Moving Objects

摘要

Coherent, homodyne, and continuous-wave radar operating with wavelengths of 3 cm, 2cm and 8 mm has been employed for collecting the radar returns obtained from moving objects. Non-stationary, nonlinear frequency modulated and multi-component radar echo responses were analyzed and described as the sum of the Doppler frequency shifted signals (polynomial chirp-like components). Instantaneous frequencies corresponding to the radar radiation scattered from different parts of a moving extended target were extracted from the short time-varying sequences of bimagnitude estimates and mapped into the time-frequency domain. Experimental investigations of the approach demonstrate clean recovery of evolutionary phase coupled harmonics for the test targets a swinging metallic sphere, and a walking person. The obtained time-frequency distributions can be used in automatic radar target recognition systems to reveal more information with new features.