A novel design tool for waveguide polarizers

This paper presents a novel method for the design of broad-band waveguide polarizers. It consists of an interactive procedure where the designer places the zeros of the reflection coefficient for one polarization, simultaneously also controlling the frequency response of the other one and vice versa. In this way, the best matching condition for both polarizations can be found. This design tool is based on an automated phase control procedure and on an algorithmic characterization of the relationship between the two frequency responses. The spurious effects of multimodal interactions, frequency dispersion, and losses are taken into account and compensated by characterizing them with suitable transfer functions. Designs of iris-loaded polarizers in square and circular waveguides are described, with operative bandwidths up to 30%. Measurements on a 10% bandwidth Ka-band prototype show reflection and cross-polarization levels of approximately -50 dB, with a phase error of approximately 0.4°.