Résumé
This paper presents the use of a circular complementary split ring resonator (CSRR) for characterizing the complex dielectric permittivity of various dielectric materials, such as polymers and biopolymers. The CSRR is etched into a ground plane and excited by a microstrip line. The CSRR is fabricated with a fast laser ablation technique, the latter providing a faster and more accessible alternative to conventional chemical etching processes. The transmission coefficient presents a shift in the resonant frequency when the resonator is loaded with a material under test (MUT). The influence on the resonant frequency of various geometrical parameters of the CSRR including substrate thickness is analyzed, providing insights for optimizing the design of a CSRR-based sensor. Then, a grounded coplanar waveguide microstrip (GCPW-MS) structure for excitation is proposed to enhance performance at high frequencies. A numerical model for the behavior of the CSRR is developed using a commercial 3D electromagnetic simulation software. The model allows to establish a relation between the resonant frequency and the permittivity of the MUT. Experimentally, a novelty presented here is that the proposed CSRR design was tested across a broad frequency range between 10 GHz and 35 GHz exceeding the frequency bands reported in the literature. The unknown permittivity of polymer materials, such as polydimethylsiloxane (PDMS) filled with carbon particles (17 and 25 %), and a biopolymer material, wheat gluten, is determined using the CSRR. Results show a good correlation between simulated and measured values of the loss factor and dielectric constant of these materials, validating the use of this CSRR for dielectric characterization in the high frequency bands. Another originality of this paper is the measurement results of CSRR showing clear resonance frequency shifts for 25 mu m thick commercial PEEK and Kapton materials, highlighting the potential of this CSRR for thin-film sensor applications.