Broadband Conductivity Measurement Technique at Millimeter-Wave Bands Using a Balanced-Type Circular Disk Resonator

We propose a broadband conductivity measurement method in the millimeter-wave bands using a balanced-type circular disk resonator (BCDR). Because of the unique feature of the BCDR's mode selective behavior over a wide band, the proposed technique can provide broadband conductivity measurements from less than 20 GHz up to over 100 GHz with a single closed-type resonator utilizing higher order mode resonances. We consider three measurement scenarios for the proposed BCDR-based broadband conductivity measurements. First, we discuss the absolute measurements of copper conductivity and then consider the relative conductivity measurements for metallic disks with reference to copper conductivity obtained in the first scenario. Finally, the second scenario is extended to the interface conductivity measurements of copper-clad substrates. The proposed measurement scenarios are demonstrated both numerically and experimentally in the millimeter-wave bands with uncertainty evaluations. The proposed technique can contribute to the development of advanced materials and implementation processes of planar circuits for various millimeter-wave applications, including 5G and 6G.