A Dual-Scale CSRRs-Based Sensor for Dielectric Characterization of Solid Materials

A compact planar sensor is presented in this letter, which could measure the dielectric constants of solid materials at microwave and sub-THz frequencies, simultaneously. The lower band resonator is based on a complementary split ring resonator (CSRR), fed by a coplanar waveguide line on the board operating at 4.76 GHz, and the upper band sensor is a 3 × 3 CSRR array, excited by a pair of WR-10 open-ended waveguide probes operating at 112 GHz. The upper band CSRR array is nested in the lower band CSRR resonator, but their sensing functions are independent of each other. A coincident sensing area is obtained that needs a testing sample with small volume. Dielectric films composed of polydimethylsiloxane and barium-titanate with different volume fractions are used to verify the performance of the sensor in both frequency scales. The advantages of the proposed design, including compact size, high sensitivity, low sample volume, and dual-scale operation, make it a competitive solution for detecting solid materials with similar dielectric properties in a single frequency band, for application such as the food industry, material quality control, and biomedical.