Measurement of complex permittivity of anisotropic dielectric spheres

Abstract

A new concept to measure the dielectric properties of anisotropic spheres at microwave frequency is presented. First, the sphere is placed in a parallel-plate microstrip structure. The anisotropic axis of the sphere is determined in a three-step process. Then, sphere is placed in a rectangular waveguide cavity resonator, where resonance modes of the sphere are excited and subsequently modeled in a field simulation tool. Simulations are matched with measurements by fitting the anisotropic complex permittivity parameters. The procedure is illustrated by determining the anisotropic axis and measuring the anisotropic complex permittivity of a sapphire sphere of 10 mm diameter.