Evaluation of conductivity for the under side section of various types of copper-clad dielectric substrates using a whispering gallery mode resonator

In this paper, the conductivity of a copper-clad cyclo olefin polymer (COP) substrate and PTFE substrates with two types of copper clad in the millimeter wave region was accurately evaluated. The roughness of the contact between the copper and dielectric could degrade the conductivity of the copper equivalently, which increases loss. The evaluation of complex permittivity in a dielectric substrate without copper was first conducted by using an open type WG mode resonator. Then the conductivity was estimated for the under side section of the substrate based upon the obtained complex permittivity by using a copper-clad type WG mode resonator. The conductivity was successfully measured for different copper-clad