Electromagnetic spectral determination of the material composition of penetrable radar targets

Abstract

The resonance theory of scattering, recently developed for the diffraction of acoustic and elastic waves¹, is applied here to radar backscattering from penetrable targets in an attempt to solve the inverse scattering problem. This means the extraction of sufficient material-composition information from the electromagnetic scattering amplitudes of the returned echoes, to permit target identification. We illustrate the principle for the case of a conducting spherical target coated with a dielectric layer. The principle of our method is to use the resonances contained in each of the partial waves making up the radar cross-section for material characterization purposes. We demonstrate that in the high frequency region, the spacing between consecutive overtones becomes uniform, and is related to the dielectric constant of the coating. The width of these overtones is proportional to the coating thickness. The resonances, therefore, make up a code that we have deciphered to solve an inverse scattering problem for penetrable radar targets of known shape, but unknown material composition.