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 Deg.