220-330-GHz Ultrawideband 90° Waveguide Twist Based on Three-Step Monoblock

This paper proposes the design of a novel ultrawideband 90° waveguide twist based on compact multiple-step structure in the 220~330GHz range. The waveguide twist is terminated by two standard rectangular waveguide ports (WR-3, 0.8636 mmx0.4318 mm). This waveguide twist employs three modified symmetric double-ridged rectangular waveguides to achieve the smooth transition of dominant mode. The in-band characteristics and polarization rotation are improved by a numerical simulation tool based on the finite element method. Within the operational terahertz frequency band, the insertion loss is optimized to less than 0.03 dB, and the return loss is greater than 20 dB. This proposed waveguide twist configuration shows great potential for scaling up to the higher terahertz frequency, which fully meets the rigorous requirements of antenna feeds and communication systems.