Discrete ARMA Model for Natural Resonances in Electromagnetic and Acoustic Scattering

Investigations of scattered transient waveforms from conducting bodies have shown that it is possible to classify electromagnetic scatterers. The concept is based upon the natural resonance modes which are part of the scatterer response to an incident excitation. A new approach for describing natural resonance modes using recursive systems is introduced. A discrete auto- regressive moving-average ARMA type model for the case of the space-time wave equation is presented. This model results from a finite-difference approximation to the wave-equation. The ARMA model has spatially-independent coefficients for the temporal recursive terms. Computed results showing aspect- and spatial- independence of natural resonance modes, with verification of the ARMA model, are also included. Applications to target identification, using the natural resonant frequencies of the targets echo signature, are considered.