Electromagnetic scattering and radiation by a circular ring and array.

摘要

An integro-differential equation for the current induced on a thin circular loop antenna in the transmit and receive modes is formulated and solved. Fourier coefficients of the ring current are evaluated using the fast Fourier transform. Asymptotic formulae are derived for the Fourier coefficients of the thin wire kernel. The total current induced on the ring by a plane wave is approximated by a modified physical optics term proportional to the incident field, plus resonant terms of lossy circulating waves. Numerical evaluation of the dominant poles and residues of the ring transfer function provides the amplitudes and complex propagation constants of these natural modes. The net aperture distribution along an axisymmetric, linear array of identical rings is separated into a combination of three physically-identifiable components: a term from the related infinite array plus contributions from two edge-effect waves. A method to extract the eigenmodes of a periodic structure is proposed.