A new method for the determination of the reflection and transmission characteristics of dielectric materials

This paper presents a new method for the determination of the reflection and transmission characteristics of dielectric materials that are the parameters for the calculation of the complex permittivity using the Nicolson-Ross-Weir (NRW) method. In transmission line methods, most widely used methods for broadband permittivity measurements, the NRW method gives a stability problem for low-loss dielectric materials near the thickness resonance frequencies. The proposed method successfully removes the problem using a relationship between the reflection and transmission characteristics. The proposed method is a new iterative transmission/reflection method applicable to permittivity measurements using arbitrary sample lengths in wide-band frequencies.

I. Introduction

Measurements of material properties in RF and microwave frequency regions have been getting more important, especially in the research fields, such as material science, microwave circuit design, absorber development, biological research, etc., as the frequency of the applications goes up to sub-millimeter wave range and the areas of the applications are being wider. Dielectric measurement is important because it can provide the electrical or magnetic characteristics of the materials, which proved useful in many research and development fields. The most widely used techniques in the microwave region are: cavity resonators, free space, open-ended coaxial probe, and transmission-line [1]–[4]. Among these techniques transmission-line techniques are the simplest methods for electromagnetic characterization in wideband frequencies for the growing number of wideband applications of various RF and microwave materials.