Complex Permittivity Measurement Method for a Dielectric Film with Low ε_r using a Millimeter-wave Circular Empty Cavity Resonator

Abstract

Next generation millimeter wave wireless devices with low profile are required. Moreover, thin dielectric substrates and low ε_r packaging materials are developed actively in order to realize such devices. Therefore, a development of a complex permittivity evaluation technique for low ε_r dielectric films in millimeter wave frequency bands is extremely expected. We focus on a circular cavity resonator which is attached conductor plate to circular cylinder for the cut-off circular waveguide method. We investigated important points for low ε_r dielectric film measurements using the circular cavity resonator. Complex permittivity of five plastic wrap films are measured at 60-GHz band to verify the usefulness for the proposed method. As a result, it is verified that it can be applied till thickness of 10 µm when resonator parameters of the ”real” empty cavity are measured accurately.