Scattering of electromagnetic pulses by simple-shaped targets with radar cross section modified by a dielectric coating

We study the scattering interaction of electromagnetic pulses with a spherical target. The target is a perfectly conducting sphere coated with a thin dielectric layer. Two different hypothetical materials are specified: a lossy dielectric and a dielectric that also has magnetic losses. The monostatic radar cross section (RCS) is computed in each case and we examine the influence of the coating on the RCS. In particular, we compare the RCS of the coated sphere with the (normalized) backscattered power when a large perfectly conducting flat plate coated with the same dielectric layer is illuminated at normal incidence by the same waveform. In particular, we find that except for frequencies below those within the efficiency band of the absorbent material, the normalized RCS of the coated sphere agrees well with the power reflection coefficient of the plate covered with the same kind of coating. For low-frequency incidences, the peaks and dips in the RCS are more prominent for the coated target than they are for the bare one. Analyzing the response of the spherical targets in the combined time-frequency domain we demonstrate that the coating itself, although reducing the RCS could introduce additional resonance features in the target´s signature at low frequencies that could be used for target recognition purposes. This observation is also confirmed by a study of the bistatic RCS of these coated objects, which we have displayed in various color graphs