Estimation of complex permittivity of arbitrary shape and size dielectric samples using cavity measurement technique at microwave frequencies

In this paper, a simple cavity measurement technique is presented to estimate the complex permittivity of arbitrary shape and size dielectric samples. Measured shift in resonant frequency and change in quality factor due to the dielectric sample loading in the cavity is compared with simulated values obtained using the finite-element method software High Frequency Structure Simulator and matched using the Newton-Raphson method to estimate the complex permittivity of a arbitrary shape and size dielectric sample. Complex permittivity of Teflon (PTFE) and an MgO-SiC composite is estimated in the S-band using this method for four different samples of varying size and shapes. The result for Teflon shows a good agreement with the previously published data, and for the MgO-SiC composite, the estimated real and imaginary parts of permittivity for four different shape and size samples are within 10%, proving the usefulness of the method. This method is particularly suitable for estimation of complex permittivity of high-loss materials.