Design of a Compact Waveguide Orthomode Transducer at Terahertz Frequency

This paper proposes the design of an orthomode transducer (OMT) based on a simple and compact waveguide structure in the 210~220GHz range. The OMT is terminated by a square waveguide common port (0.8636 mm×0.8636 mm) and two standard rectangular waveguide ports (WR-3, 0.8636 mm×0.4318 mm). This OMT employs a symmetric polarization separating junction to realize the simultaneous propagation of two orthogonally polarized modes, which requires no septums or pillars. The impedance-matching characteristics and cross-polarization effect 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 0.2 dB, and the average isolation of two orthogonal modes is below -52 dB.