Electromagnetic scattering by slots on a sphere

The scattered field when a plane wave is incident on a slotted perfectly conducting sphere is obtained by superposition of the scattered field from an unslotted sphere and the radiation field from the slot on the sphere. The slot is a finite, thin circumferential slot backed by a cavity which is characterised by an admittance. The induced voltage is represented by a sinusoidal distribution. The amplitude of the induced voltage is then related, in the combined problem, to the incident field by expressing it in terms of the radiating and load admittance of the slot. Expressions for the radiation admittance and the scattered fields are derived. Positions of slots with respect to the orientation of the incident plane wave which give rise to maximum or minimum scattering are discussed. Various special cases, such as the half-circumferential slot and the full-circumferential slot, are also derived.