Sensor and Methodology for Determining Dielectric Constant Using Electrically Coupled Resonators

In this letter, a new sensor, theory, methodology, and experimental results of dielectric constant characterization of several planar samples under test (SUT) are presented. Each SUT is placed over a microstrip sensor that is based on a pair of electrically coupled resonators (ECRs). The proposed method determines the dielectric constant by using the electric coupling coefficient ( $k_{e}$ ) of a pair of coupled half-wavelength open-loop resonators. The methodology was successfully tested over a wide dielectric constant value substrates at 2.5 GHz, with substrates Diclad 880, Rogers 5870, Rogers 4003C, TMM10i, and Rogers 6010 resulting in high-accuracy percentages of 99.22%, 99.21%, 99.56%, 97.68%, and 98.60%, respectively.