Metamaterial-inspired microwave sensor for measurement of complex permittivity of materials

ABSTRACT This article presents the design and development of a metamaterial inspired planar microwave sensor for the measurement of complex permittivity of the solid and liquid sample under test (SUT). A hexagonal complementary split ring resonator (CSSR) is etched on the ground plane of a 50 Ω microstrip line, which is excited by the electric field component normal to the ground plane. The proposed hexagonal sensor possesses a good sensitivity, and the SUT placed over the CSSR perturbs the electric field associated with the CSRR giving rise to a change in the resonance frequency and peak attenuation of the transmission coefficient under loaded condition. An empirical relation between sensor resonance characteristics and the complex permittivity of the SUT is derived to determine the complex permittivity of the SUT. The designed sensor is fabricated on an FR4 substrate and is experimentally validated for various standard solid samples and hazardous chemical liquids. The proposed sensor is working in the frequency range of 5.3–8.2 GHz and is capable of measuring a number of samples with their dielectric properties varying over a wide range. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2577–2581, 2016