170-260-GHz Ultrawideband and High Isolation Orthomode Transducer Based on Symmetric Reverse Coupling Structure

In this article, we propose a novel ultrawideband orthomode transducer (OMT) with high isolation. This novel OMT is designed based on a symmetric reverse coupling structure, which employs two forms of double ridges to replace the pillars or septums that are difficult to process. In this way, the OMT achieves simpler double symmetry structure with higher tolerance capability and lower processing difficulty. In addition, the impedance-matching characteristics within the waveguide are optimized by the symmetrical double-ridged structure, allowing wider bandwidth and higher isolation to be obtained than in conventional structures. To confirm the theoretical results, a WR-4.3 full-band OMT was processed by computer numerical control (CNC) milling technology with 10- \mu \text{m} precision. Measurement results show that in the 170-260 GHz range, the average return loss (RL) is 24 dB, the average insertion loss (IL) is 0.6 dB, and the average isolation is 54 dB. The measured results are strongly in agreement with the simulation results.