Reducing standing waves in quasi-optical systems by optimal feedhorn design

Standing waves between transmit and receive feedhorns in quasi-optical systems often limit the achievable performance of mm-wave and sub-mm-wave instrumentation. Even with high performance corrugated feedhorns and perfect frequency independent optics, significant standing waves can occur because of the resonant build-up of higher order modes between feedhorns. In this paper we describe a new design of wideband corrugated feedhorn that significantly reduces standing wave effects, is scalable to any frequency, is shorter than standard horns and is suitable for a wide range of optical configurations. In addition it produces far-field beam patterns with much reduced sidelobes. We will describe the theory behind this new feedhorn design, outline scaling laws and present experimental results confirming the analysis.