Electromagnetic backscattering from objects with micro-motion dynamics is subject to modulations that result in periodic time-varying Doppler spectra about the carrier frequency. The characteristics of the spectra enable us to determine dynamic properties and provide useful information about the objects.
Fourier transform is the most common method to analyze the properties of a signal waveform in the frequency domain. However, due to lack of localized time Information, it cannot provide more detailed information on time-varying frequency modulation. The most suitable method to observe time-varying micro-Doppler spectra is the time-frequency transform that provides localized time-dependent Doppler frequency information.
In this talk, we first briefly describe physics of electromagnetic backscattering from objects undergoing motion dynamic and discuss simulations of backscattering using computational electromagnetic (CEM) modeling. Then, we apply CEM tools to an object with complicated nonlinear motion dynamics, and discuss how to analyze the time-varying micro-Doppler spectrum. It shows that object's dynamic micro-motions can be well characterized by its time-varying micro-Doppler spectrum that can be used to identify distinctive object features.