Investigation of Electromagnetic Mode Transition in 220-325-GHz Horn-type Connector

This paper presents a comprehensive study of the electromagnetic mode transition in a horn-type connector for terahertz (THz) applications using simulation in the CST Microwave Studio Suite. This simulation focuses on analyzing the mode conversion and electromagnetic field characteristics within the connector. The main objective is to study the mode transition from the TE 10 mode in the WR-3 rectangular waveguide (RWG) as it propagates into the horn connector. In particular, the mode conversion from the TE 10 mode to other TE and TM modes, with vertical and horizontal polarizations, was investigated. In the case where port 1 is a WR-3 RWG operated in TE 10 mode with vertical polarization, it has been found that TE 11 mode with vertical polarization is well suited to be output at port 2. This mode maintains the same polarization as the TE 10 mode at port 1, ensuring a smooth transition and minimal power loss during mode conversion. In contrast, the competing modes are relatively unsuitable. The connector dimensions are designed and optimized for the TE 10 mode with vertical polarization, and the presence of other competing modes results in undesirable reflections, scattering, and excitation of higher-order modes. The simulation results show that the insertion loss of the TE 11 mode with vertical polarization is close to zero, indicating that the connector has an extremely efficient signal transmission with minimal power loss in the THz frequency range of interest.