Material Characterization Innovations in Microwave Measurement Laboratory of Amirkabir University of Technology

This paper presents some microwave circuits, designed for characterization of materials’ permittivity. These include single and multiple-resonant types, transmission line approaches, radiation structures and planar circuits. They have either theoretical analysis, simulations, behavior analysis, or fabrication results. A simple half-wavelength coaxial system is used for measuring velocity factor or dielectric constant of the cable. This method presents very accurate results. A planar multi-dielectric antenna structure is proposed whose layers comprise the dielectric under test. The near field as well as the radiation performances are influenced by the permittivity, which is the basis for determining this parameter. Also, a planar resonant cavity is designed and optimized to give enhanced coupling performance and gets higher quality factors. It has a small size and its sensitivity is improved employing a chamfer. The values of dielectric constants are extracted from scattering parameters. In another method, a three-section microstrip line is used whose time domain response is employed to retrieve the dielectric constant. This method can be generalized to other planar lines. At last, a simple method for measuring complex conductivity of lossy planar conductors is studied and it is employed for characterization of a graphene oxide layer.