A Compact TM 01 -to-TE 10 THz Mode Transducer With High Suppression of Spurious Modes

In this letter, a high-mode-purity TM01-to-TE10mode transducer operating at 340 GHz is designed, which has great potential in terahertz (THz) power combining. A compact configuration and high mode purity are realized through the integration of a five-step septum and an impedance matching structure within the transducer. By adopting a well-optimized septum and transition structure, high suppression of spurious modes (TE11, degenerated TE11mode) greater than 50 dB can be achieved, resulting in a TM01mode purity as high as 99.9%. Notably, the septum-based transducer enables same-direction mode conversion from TM01to TE10, which significantly simplifies subsequent assembly and enhances overall system integration. A back-to-back prototype of the transducer operating in the 310–355 GHz range was fabricated and tested. The measured results show that within the frequency range, the overall average insertion loss of single transducer is approximately 1.55 dB (1.5dB at 340 GHz), and the return loss of the input port is better than 10 dB.