Capacitively-Coupled Resonators for Terahertz Planar-Goubau-Line Filters

planar Goubau lines show promising potential for terahertz (THz) applications. However, a single-wire waveguide exhibits less design freedom than standard multiconductor lines, which is a significant constraint for realizing standard components. Existing filters for planar-Goubau-line lack clear design procedures preventing the synthesis of an arbitrary filter response. In this work, we present a design for a bandpass/bandstop filter for planar Goubau line by periodically loading the line with capacitively-coupled lambda/2 resonators, which can be easily tuned by changing their electrical length. The filter's working principle is explained by a proposed transmission-line model. We designed and fabricated a passband filter centered at 0.9 THz on a 10-mu m silicon-membrane substrate and compared measurement results between 0.5 and 1.1 THz to electromagnetic simulations, showing an excellent agreement in both S-11 and S-21. The measured pass band has an insertion loss of 7 dB and a 3-dB bandwidth of 31%. Overall, the proposed filter design has a good performance while having a simple design procedure.

Automated summary

Planar Goubau lines show promise for terahertz (THz) applications, but existing filters lack clear design procedures. In this study, we propose a design for a bandpass/bandstop filter by periodically loading the line with capacitively-coupled lambda/2 resonators. The filter's working principle is explained using a transmission-line model. We fabricated and tested a passband filter centered at 0.9 THz on a 10-µm silicon-membrane substrate, demonstrating good agreement between measurements and simulations.