Electromagnetic scattering by a metallic spheroid using shape perturbation method

The scattering of a plane electromagnetic wave by a perfectly conducting prolate or oblate spheroid is considered analytically by a shape perturbation method. The electromagnetic field is expressed in terms of spherical eigenvectors only, while the equation of the spheroidal boundary is given in spherical coordinates. There is no need for using any spheroidal eigenvectors in our solution. Analytical expressions are obtained for the scattered field and the scattering cross-sections, when the solution is specialized to small values of the eccentricity h = d/( 2a), ( h << 1), where d is the interfocal distance of the spheroid and 2a the length of its rotation axis. In this case exact, closed-form expressions, valid for each small h, are obtained for the expansion coefficients g(( 2)) and g(( 4)) in the relation S( h) = S( 0)[ 1 + g(( 2)) h(2) + g(( 4)) h(4) + O( h(6))] expressing the scattering cross-sections. Numerical results are given for various values of the parameters.