Design and Fabrication of Narrow-Band Waveguide Resonators near 380 GHz

This work addresses the design and fabrication considerations of sub-terahertz narrow-band resonators for high performance and low-cost manufacturability. The intended application of these resonators is to realize narrow-band filtering for passive millimeter-wave sounding of upper tropospheric humidity using the 380 GHz water vapor absorption line. Various narrow-band filter designs and manufacturing processes have been considered. The inductive iris waveguide design was chosen for manufacturing. This design yields a resonator response and reliably achieves a bandwidth narrower than 3 percent around 376 GHz. This design and the fabrication technique validate the use of lower-order filter and resonator structures to achieve narrow bandwidths. The experimental results are presented and compared with other recently fabricated filters above 200 GHz.