Solid and Non-Solid Dielectric Material Characterization for Millimeter and Sub-Millimeter Wave Applications

An accurate quasi-optical S-parameter measurement method implemented in the normalized frequency bands Ka, W and J is presented in this paper. Permittivity extraction of various solid or non-solid dielectric materials is performed using the 4 S-parameters without time domain gating nor filtering. The procedure is validated through the comparison between the simulated and measured 4 S-parameters in magnitude and phase. Results are given for the Rexolite over a wide frequency span from the Ka to J band while some non-solid materials were characterized in the W band. Moreover, effects of rain flow on a dielectric slab were investigated for automotive radar applications in the W band and preliminary results are given.

I. Introduction

Millimeter waves up to THz are increasingly being used or foreseen in various applications such as 5G (backhaul), RFID tags to analyze the risks associated with aging structures, imaging for non-destructive control and security, automotive radars, radiometry,… Knowledge of the complex dielectric permittivity of materials is essential to achieve the specifications in the design of devices and systems at very high frequencies. Moreover, the study of the propagation and the interactions of waves with the environment also requires a detailed knowledge of these characteristics. Material characterization can be performed in a rectangular or coaxial waveguide, or in a cavity, where machined samples are inserted. Due to very small dimensions of the waveguides at millimeter waves and very small frequency bandwidth extraction in cavities, free space non-resonant techniques are preferred at very high frequencies [1].