Terahertz low-pass filter based on cascaded resonators formed by CPS bending on a thin membrane

A membrane-based coplanar-stripline (CPS) transmission-line platform has recently enabled implementation of diverse THz system-on-chip (TSoC) components. In this paper, we demonstrate an elliptic-function THz low-pass filter (TLPF) using cascaded λ/4 resonators between the right-angle bending of a CPS transmission line defined on a 1 μm-thin membrane. We investigated the effect of bending the CPS transmission line with different angles that introduces a frequency response similar to a simple LC low-pass filter (LPF) and facilitates the design of a desired roll-off performance using traditional methods. ANSYS HFSS was used to provide a full-wave analysis and characterize the effective parameters of the TLPF with a designed cutoff-frequency around 0.6 THz. Using 7 sections of right-angle CPS bending with total length 1.4 mm, we demonstrate experimentally an elliptic-function TLPF characterized by a low-ripple at passband, a roll-off transition with zero transmission near the cutoff frequency and a wide stopband with -60 dB rejection.