A nondestructive method for measuring the complex permittivity of dielectric materials at microwave frequencies using an open transmission line resonator

The method is based on perturbing the fringing field at the open end of the transmission line by an unknown dielectric material, and is applicable not only for solid dielectric materials but also for liquids and gases. Forming or shaping of solid dielectrics is not required, but there should be a small area available for contact. Thickness of the dielectric material terminating the line does not affect the measurement unless the material is thinner than twice the spacing between conductors of the coaxial line. The experimental results obtained for some solid dielectric materials, liquids, and biological tissue shows that the method has sufficient accuracy for most applications up to about 4 GHz.