Microwave Surface Conductivity Measurement Using an Open-Ended Circular Waveguide Probe

A microwave surface conductivity measurement method, using an open-ended circular waveguide, is proposed, electromagnetically simulated and experimentally verified. The proposed method utilizes an open-ended circular waveguide excited with the TE01 mode radiating into a resonant single layer conductor-backed dielectric structure. By conducting reflection coefficient measurements of the structure over a range of frequencies, a resonance can be identified and used to closely estimate the conductivity of the backing conductor, providing for an in-situ microwave conductivity measurement method. The properties of the structure are chosen to provide good sensitivity over a wide range of conductivities. The effect of a nonzero loss factor for the dielectric layer is also analyzed. Subsequently, a TE01 mode circular waveguide probe was designed, fabricated and used, along with a quartz sheet acting as the dielectric layer, to measure the surface conductivity of various conductors in the 32-40 GHz range.