Evaluation of effective conductivity of copper post and transmission losses of post-wall waveguide in millimeter wave band

This paper presents a measurement method for determining the effective conductivity σ_p of copper posts in a copper-clad dielectric substrate in the millimeter-wave region. The conductivity is indirectly evaluated from measured resonant frequencies and unloaded Q values of a number of Whispering Gallery modes excited in a post-wall circular resonator with a large diameter of 10 - 30 wavelengths. We measure σ_p in 40 - 51 GHz band. The measured σ_p of the copper post decreases with the increase in the frequency. We confirm the measured results by comparing between the calculated results and the measured results of transmission losses for post-wall waveguides.