Demonstration of a planar multimodal periodic filter at THz frequencies

This paper presents a planar multimodal periodic filter that is constructed from alternating sections of coplanar stripline and the odd-mode of a finite-ground plane coplanar waveguide constructed on a 1 um silicon nitride substrate to facilitate operation at THz frequencies. The multimode configuration differs from standard single-mode periodic filters and enables flexible designs and the possibility for active control of the filter characteristics. For this proof-of-concept, we present the relevant theory and design procedures required to develop a band-stop filter that has a center frequency of fc = 0.8 THz and a bandwidth of df = 0.07 THz. We find good agreement between theory, simulation, and experiment.