Design of a Compact 3-D Metal Printed Ka-band Waveguide Polarizer

This letter presents design, development, and characterization of compact wideband three-dimensional (3-D) printed circular waveguide-based polarizer operating in Ka-band (28-34 GHz). The polarizer structure is investigated using fundamental and higher-order modes, based on which a simplified equivalent structure is derived, giving physical insight into its mechanism of operation. The design consists of a pair of radially opposite grooves inside a circular waveguide and excited using a coaxial probe, which makes the design simple and highly compact as compared to other conventional circular polarizers. The design is compared with other existing waveguide-based polarizers in terms of electrical and physical parameters. Fabrication is done using high-resolution direct metal aluminum 3-D metal printing. The measured axial ratio is better than 3 dB over the frequency band. The design simplicity makes it attractive for application in millimeter-wave frequencies and beyond.