Non-contact measurement of permittivity and thickness using planar resonators

This paper presents a single compound complementary split-ring resonator (SC-CSRR) to induce three resonance frequencies for non-contact measurement of the permittivity and thickness of a material. By using the proposed method, the derived relationship function of the resonance frequencies can be used to determine the thickness and the permittivity of the material under test (MUT) with various air gaps existing between the sensor ground plane and MUT. A simple and low-cost SC-CSRR measurement method for assessing the thickness and the permittivity of materials in a non-contact method was numerically analyzed and experimentally verified. At the air gap of 0.2mm, the experiments yielded average measurement errors of 4.32 % and 5.05 % for the thickness and permittivity, respectively.