Waveguide Linear-to-Circular Polarization Converter With Cross Polarization Below −40 dB Within 16% Band

A passive waveguide component with circular input and output ports that converts the incident TE
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mode polarization from circular to linear and vise versa (a polarizer) is under investigation. Compared with a number of previous researches on this topic, including structures with elliptical, rectangular, truncated cross sections, and rectangular waveguides with periodically perturbed walls, the problem of realization of an ultralow cross-polarization factor (below −40 dB) within the maximum bandwidth is theoretically analyzed in detail based on dispersion evaluation. The solution in the form of a rectangular structure with a pair of corrugated walls with precise mechanical adjustment was manufactured and measured yielding the bandwidth of 16%. A polarizer with such characteristics is extremely important when served as an element of a microwave system for input–output through one window of a high-power high-gain gyrotron traveling-wave tube (gyro-TWT) with a helically corrugated waveguide.