A corrugated wave-guide feed for discrete multi-band applications having dual depth corrugations

A feed with dual depth corrugations (DDC) has been considered in view of the following observations in a conventional corrugated feed. Corrugated feeds have good radiation characteristics over a bandwidth in which the surface admittance of the corrugations is capacitive. A sudden deterioration of radiation characteristics is observed due to the on-set of surface waves supported by an inductive surface reactance. The slot admittance of the corrugations in a conventional corrugated feed is capacitive over an actave bandwidth. In a feed with DDC it has been observed that the on-set of surface waves can be suppressed and as a result the desired radiation behaviour is extended to lower frequencies where the surface admittance is inductive.