An Improved Algorithm for Deducing Complex Permittivity of Thin Dielectric Samples with the Transmission/Reflection Method

Transmission/reflection method is widely used in microwave engineering for determining dielectric properties of materials, and significant uncertainty will arise in the results if the thickness of the samples is small. In this paper, we propose an improved algorithm for deducing complex permittivity of thin dielectric samples with the transmission/reflection method. With the proposed algorithm, the real and imaginary parts of the complex permittivity will be treated separately, and two independent weighting factors, beta(re) and beta(im), will be used to minimize the uncertainty in both parts of the complex permittivity. Numerical calculations as well as experimental measurements on undoped and borondoped diamond films were conducted within the frequency range of 18.5-26.5 GHz to demonstrate the effectiveness of the algorithm. It is verified that among the various iterative algorithms which could be used to derive complex permittivity, the proposed algorithm is the most advantageous in reducing uncertainties when thin dielectric samples are dealt with.