Ultra-Wideband 90° Waveguide Twist for THz Applications

We report on the design, fabrication, and characterization of a novel 90° waveguide step twist with 56% fractional bandwidth. The proposed twist provides 90° field rotation in the frequency range 210–375 GHz. The experimental results are in good agreement with the electromagnetic simulations showing an insertion loss below 0.3 dB and a return loss better than 20 dB over most of the band. The ultra-wideband performance, tolerance to fabrication inaccuracies, and compactness makes the proposed design attractive for various mm and submillimeter applications. The twist geometry is optimized for simple fabrication through direct milling. Furthermore, the design remains highly compact since both steps are fabricated on a single washer.