Complex Permittivity Characterization of Low-Loss Dielectric Slabs at Sub-THz

TL;DR

This paper introduces a new quasi-optical method for accurately measuring the complex permittivity of low-loss dielectric slabs at sub-THz frequencies, surpassing previous approaches in precision.

Contribution

A novel measurement algorithm for sub-THz permittivity characterization of low-loss dielectrics with improved accuracy demonstrated through simulations and comparisons.

Findings

High measurement accuracy for thick dielectric slabs (error 0.1%)

Lower accuracy for thinner slabs (error <5%)

Method outperforms previous approaches in accuracy

Abstract

This manuscript presents a novel method for characterizing the permittivities of low-loss dielectric slabs in sub-terahertz (sub-THz) frequencies, specifically above 100 GHz using a quasi-optical system. The algorithm is introduced with detailed derivations, and the measurement sensitivity is analyzed through simulations. Subsequently, the method's validity is established via simulations, demonstrating high accuracy (error 0.1% for the loss tangent) for a 30 mm thick plate material and relatively lower accuracy (error <5% for the loss tangent) for a 6 mm thick plate material. Notably, this accuracy surpasses that of the approach presented in [1] when the same window width is used to extract signals. Furthermore, a comparison between the permittivities of plexiglass with a 30 mm thickness characterized by the proposed method and the approach in [1] reveals a maximum difference in the dielectric constant of 0.011 and in loss tangent of 0.00071 from 140 to 220 GHz. Finally, the relative complex permittivities of plexiglass at 142.86 GHz obtained by both methods are compared with the reference values provided in [2], exhibiting differences of 0.06 in the dielectric constant.