The Effects of the Dielectric Substrate Thickness and the Loss Tangent on the Absorption Spectrum: A Comprehensive Study Considering the Resonance Type, the Ground Plane Coupling, and the Characterization Setup

Abstract

In this study, the effects of dielectric substrate thickness and the dielectric loss tangent on the absorption spectrum are investigated parametrically in S-band. The study has been conducted on two different absorber topologies, one is closed ring resonator (CRR) and the other is composed of a split ring resonator (SRR), to observe the effects on both LC- and dipole-type resonances. The studies on the substrate thickness have been performed both numerically and experimentally, whereas the studies on the dielectric loss tangent have been performed numerically. The results agree with the literature such that the substrate thickness has significant effects on the resonant frequency and the absorption peak level which is explained by the impedance matching phenomenon. Besides, we show that the frequency shift behavior (i.e. redshift or blueshift) in response to substrate thickness change highly depends on the coupling between the resonator structure and the metallic ground plane. Moreover, the responses of absorption spectra to the changes of substrate thickness and dielectric loss are very similar whether it is due to an LC or a dipole-type resonances. We believe that the comprehensive and systematic parametric analyses in whole contributes to the literature especially considering the experimental studies in microwaves.