Design and Measurement of a Terahertz Band Rectangular TE 20 Mode Power Coupling Structure for High-Order Overmoded Multiple Sheet Electron Beam Devices

A novel methodology of the power coupling from rectangular TE10 mode to TE20 mode for high-order overmoded multiple sheet electron beam devices is presented in this letter. The mode conversion was realized by an H-plane T-junction based mode converter with E-plane symmetric matching steps and the beam wave convergence/separation was realized by an overmoded Y-shaped coupler with a Bragg reflector. To verify the idea, two identical H-band (220-325 GHz) power coupling structures joined back-to-back were designed and manufactured by nano computer numerical control machining. The measured transmission and reflection coefficients were respectively ~ −2.0 dB and ~ −10.0 dB in the frequency range of 250.0-294.0 GHz.