60 GHz square open-loop resonator (SOLR) based on planar Goubau line (PGL) technology

This study presents the design, fabrication, and measurement of a square open-loop resonator (SOLR) on high resistivity silicon substrate feed with a planar Goubau line (PGL), which is a very low-loss transmission line around 60 GHz fabricated through a very simple and low-cost process. Electromagnetic simulations using ANSYS high frequency structure simulator are performed for the PGL structure, in order to determine the PGL characteristics (impedance, losses and quality factor) versus the line width. The geometrical parameters of the SOLR structure are studied to observe their impact on reflection and transmission properties. An equivalent lumped element circuit is extracted from the distributed planar design to study and optimise the resonating structure using Advanced Design System. This electrical circuit response is successfully compared to the planar electromagnetic structure one, and a parametric study permits to better understand the role of the different circuit elements. Field displays lead to a better understanding of the SOLR behaviour. For measurement purpose of the fabricated structure, a coplanar waveguide-PGL transition is optimised with 0.9 dB losses. Simulation and measurement results show good performances for filter applications with 1 dB losses and small size at 60 GHz for 10% bandwidth.