Design of SRR-Based Microwave Sensor for Characterization of Magnetodielectric Substrates

A novel split-ring resonator (SRR)-based microwave sensor for accurately determining the real parts of the complex permittivity and the complex permeability of magnetodielectric composites is proposed. The proposed sensor is realized using the microstrip technology, where two SRRs coupled magnetically with the microstrip line are printed on two sides of the line. The sensor is designed using the full-wave electromagnetic solver and its equivalent circuit model is obtained. A numerical model of the proposed sensor is developed for extracting the magnetic and the dielectric properties of the sample under test in terms of change in resonance frequency after loading the device with the test specimen. The proposed methodology is validated by fabricating the sensor on RT/duroid 6006 substrate and testing various standard dielectric and magnetodielectric samples viz. Teflon, Poly vinyl chloride, Plexiglas, Polyethylene, Carbonyl iron, Ni0.6Co0.4Fe2O4, and Cobalt (30%)/Polystyrene composite in S-band. The measured relative permeability and the relative permittivity of the test specimens are found to be in close agreement with their values available in literature with maximum error of less than 8%.