Enhancing the Sensitivity of Dielectric Sensors With Multiple Coupled Complementary Split-Ring Resonators

This article presents a new concept for sensitivity enhancement of dielectric sensors by loading a microstrip line with multiple coupled resonators. The concept is based on the interresonator coupling mechanism, which is represented as a mutual capacitance in an equivalent lumped circuit model. This mutual capacitance increases the sensitivity of the sensor (in terms of a shift in the resonance frequency) to detect the presence of dielectric materials (i.e., detecting changes in the real-relative permittivity of dielectric laminates). Complementary split-ring resonators (CSRRs) are utilized and coupled to a splitter-combiner microstrip section to design a 2CSRR and a 4CSRR sensor. The new sensors provided an appreciable enhancement in the sensitivity when detecting dielectric material. The concept is tested using full-wave numerical simulations to detect variations in the dielectric constant of a slab. Finally, full experimental validation is provided using fabricated sensors.