Bandpass Filters Based on Coupled Split Ring Resonators for Surface Waves on Planar Goubau Lines

This paper demonstrates a method for enhancing the performance of recently introduced compact bandpass filters for terahertz surface waves on single wire waveguides, the so-called planar Goubau lines (PGLs). It is firstly shown numerically and validated experimentally that a gapped PGL loaded with a pair of split ring resonators (SRRs) acts as a bandpass filter. The concept and simulation result are validated through experiment. Furthermore, in order to achieve an improved frequency response, a third-order filter based on coupled SRRs is proposed. It is shown that while the size of the proposed filter is further reduced, it additionally benefits from a higher in-band transmission, improved selectivity, and a controllable wide bandwidth.