Multifunctional Dual-Band Microwave Sensor for the Detection of Liquid Permittivity and Solid Displacement

This study proposes a dual-band microwave sensor based on a split-ring resonator (SRR) coupled with a pair of L-shaped structures. The proposed sensor has dual functionalities, including the detection of liquid permittivity and solid displacement. An ethanol-water mixture is selected as a sample to measure the permittivity of the liquid. Moreover, FR4 is chosen as the test sample to measure the displacement of the solid. As a result, the maximum frequency detection resolution (FDR) is 1.64, and the average FDR is 1.40. The maximum and average normalized sensitivity (NS) values are 0.073% and 0.06%, respectively. The maximum displacement sensitivity is 10.0 MHz/mm for f_DS2 and 10.5 MHz/mm for f_DS1, while the average displacement sensitivity values are 4.98 MHz/mm and 8.02 MHz/mm for f_DS2 and f_DS1, respectively. These values confirm the sensor’s reliable performance and sensitivity across different measurements. In general, the proposed sensor offers several advantages: 1) it operates independently by isolating the electric fields generated by each sensor; 2) it demonstrates dual functionalities, including the detection of liquid permittivity and solid displacement; and 3) it is capable of handling both liquid and solid samples.