CSRR Based Sensors for Relative Permittivity Measurement With Improved and Uniform Sensitivity Throughout [0.9–10.9] GHz Band

Abstract

This paper proposes miniaturized, lightweight and high sensitivity planar metamaterial based sensors for relative permittivity measurement within [0.9–10.9] GHz band. Each proposed sensor is designed using a thin-substrate microstrip line loaded with a single complementary split ring resonator (CSRR). The loaded resonator is excited using maximum electric/magnetic (cross polarization) excitation to maximize the sensors’ sensitivity. Each proposed sensor operates at different frequency range within [0.9–10.9] GHz band based on the size of the loaded resonator. Compared to similar state-of-the-art sensors, the proposed ones are at least 30% more sensitive. The minimum transmission frequency shifts (50)% as the sample’s relative permittivity changes from 1 to 10. The paper proposes a condition of sensitivity uniformity to maintain a uniform sensitivity over the specified band irrespective of the resonator size. Utilizing the proposed condition, the sensitivity of all sensors remains uniform throughout [0.9–10.9] GHz band for all dielectric samples with relative permittivity between 1 and 10. This vital feature allows the practical realization of resonant probes with less computational operations and consistent measurements over a wide dynamic range of the sensing-related frequency. Experimental measurements are in good agreement with the numerical findings. The paper includes a comprehensive sensitivity analysis which investigates the effect of resonator’s excitation scheme, resonator’s order (i.e. single or double CSRR) and substrate thickness on the sensitivity of CSRR based sensors. The proposed sensing platforms are recommended for the development of highly sensitive, consistent and reliable planar sensors such as microfluidics, displacement, nondestructive and biomedical sensors.