Microwave filter response of nonuniformly corrugated circular waveguide

Abstract

A corrugated circular waveguide is proposed as a microwave filter. The analysis is carried out using the perturbation method of multiple scales for the case of TM modes. The analysis concerns the interaction of two and four modes satisfying the resonant condition (Bragg condition) imposed by the periodicity of the waveguide wall. The coupled mode equations derived via the method of multiple scales are used to formulate the filtering problem as a two-point boundary-value problem which is solved numerically. Desirable filtering characteristics may be realised by introducing tapered as well as chirped corrugations to control the frequency response of such a wave filter. In case of two-mode interaction the side ripples can be eliminated by tapering the waveguide wall. In the four-mode interaction case, a multichannel filter may be realised by combining taper and chirp.