A 325–500-GHz Waveguide Balun With Polarization Twist Characteristics for THz Integrated Circuits and Systems

In this article, a waveguide balun with additional polarization twist characteristics for terahertz (THz) integrated circuits and systems is proposed and demonstrated. Unlike traditional waveguide baluns, this novel balun enables the polarization ration from an E-plane waveguide input to two H-plane waveguide outputs without requiring any additional circuit components, achieving an out-of-phase performance at the output ports. Typically, such a functionality would require an E-plane waveguide power divider combined with two traditional waveguide twists and a 180° phase shifter, which significantly increases the design complexity, circuit size, and associated losses. The proposed balun offers a distinct advantage in multiway polarization waveguide systems through structure simplification and loss minimization. To verify and validate this twist topology, a 320–500-GHz experimental prototype is designed, fabricated, and measured. Measured results confirmed an excellent performance of the proposed waveguide twist. The prototype achieves a compact length of only $0.4\lambda $ , where $\lambda $ represents the wavelength at the center frequency. Therefore, the proposed balun stands for an excellent candidate for compact and broadband THz waveguide circuits and systems.