A High-Sensitivity Microwave Antenna Sensor Using Complementary Split Ring Resonator for Non-Invasive Permittivity Characterization of Dielectric Material

This paper proposes a novel high-sensitivity planar microwave antenna sensor for non-invasive permittivity characterization of dielectric materials. The sensor is constructed using a planar dual-band antenna loaded with a complementary split-ring resonator (CSRR). The CSRR structure is etched on a circular monopole patch, which can be easily activated by using a simple microstrip network, offering the advantage of supporting dual resonant frequencies. In the measurement, the dielectric sample is easily placed on the top surface of the antenna-based sensor, enabling non-invasive permittivity sensing by observing the resonant frequency variations across different operating bands of the sensor. Simulated results demonstrate the effectiveness of the proposed microwave antenna-based sensor in monitoring the variations in relative permittivity across different resonant frequencies. Additionally, the sensor exhibits high sensing sensitivities of 149.15 $\mathbf{MHz}/(\Delta\varepsilon_{rd}=1)$ and 130.13 $\mathbf{MHz}/(\Delta\varepsilon_{rd}=1)$ for the lower and higher resonant frequencies, respectively.