Scattering of short EM-pulses by simple and complex targets in the combined time-frequency domain using impulse radar

Using targets of either simple or complex geometrical shape, the scattering of electromagnetic pulses of short duration was studied both theoretically and experimentally. The experiments were performed using an impulse radar system. The targets of complex shape were plastic scale models of two aircraft with metallized surface. For comparison, targets of simple shape were also used. The form-function in the backscattering direction, determined from measured data when the targets are illuminated at a few different aspects, the signature representations of targets are extended to the combined time-frequency domain, and the physical basis of the signature features in the form-function using short-time Fourier transforms is discussed. By computing and displaying pseudo-Wigner distributions of recorded transient responses it is demonstrated that the time-frequency signature as given by the pseudo-Wigner distribution can extract and exhibit informative features in the frequency band of the incident pulse in agreement with the time development of resonance features.