Natural-mode representation of transient scattering from rotationally symmetric bodies

A procedure for calculating the natural frequencies and the current distribution of the natural modes of a perfectly conducting body of revolution is presented. The analysis is based on the magnetic-field integral equation simplified to account for rotational symmetry. A technique is developed for the numerical evaluation of the natural frequencies and modes of a perfectly conducting rotationally symmetric body. The technique is used in a numerical sample calculation of natural frequencies and modes of a prolate spheroid. The general method of treating transient electromagnetic scattering problems developed previously is specialized to perfectly conducting bodies of revolution. In particular, scattering of a step-function plane wave from a prolate spheroid is treated numerically. The time response of the induced surface current is constructed from the natural modes in the same way as in network theory. The convergence of the solution, as the number of modes is increased, is also considered.