Terahertz Side Arm Orthomode Transducer with High Isolation and High Cross-polarization Discrimination

This paper presents a terahertz side arm orthomode transducer (OMT) with high isolation and cross-polarization discrimination (XPD). The structure of the OMT is based on the simplest orthogonal side arm design, but with the introduction of a mirror waveguide structure, which breaks the single symmetry limitation of the traditional orthogonal side arm structure, the OMT gains double symmetry and thus achieves superior isolation and XPD. At the same time, by using a simple matching waveguide, the OMT achieves a wider bandwidth without increasing the complexity of the structure. The proposed OMT has a working bandwidth of 190-230 GHz, with a return loss of less than -15 dB, an isolation of less than -85 dB, and an XPD of less than -77 dB across the entire bandwidth. Compared with other OMT structures with double symmetry, such as turnstile junction and double-ridged waveguide, the proposed OMT structure is more compact and simpler, greatly reducing the difficulty of processing and manufacturing and having better tolerance capability.