Electromagnetic Wave Propagation Through Chaff Clouds

The computation of electromagnetic wave scattering by clouds of dipoles is straightforward when the dipole density is small. For higher density clouds, the coupling effects between the dipoles and their attenuation effects on the wave must be considered. This is accomplished herein by replacing the randomly distributed dipoles in the cloud by a conducting continuum. The conductivity of this continuum is determined by requiring that the radar cross section (RCS) of an infinitesimally thin slab of the continuum be the same as that of a similar portion of the dipole cloud. The thinness of this reference dipole cloud eliminates the necessity to consider inter-dipole coupling. The reflection and transmission characteristics of the cloud are then obtained using standard methods for propagation through the effective conductor. RCS results are shown to agree with coupled numerical integral equation solutions for scattering from a closely spaced system of wires. Simple formulas are derived for the attenuation effects of the dipole cloud. For most cases of interest, the wave with wave length lambda attenuates through a cloud of half wave dipoles of density p at the rate of 0.655 (plambda³) dB per lambda.