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 1,1 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.