Dual band RF sensor for testing of magnetic properties of materials using meandered line SRR

In this paper, a microwave planar resonant sensor using the meandered line based split ring resonator (MLSRR) is proposed to retrieve the magnetic properties of materials in 3G and 4G GSM bands. The proposed sensor is based on the field perturbation theory, where the permeability of the test sample is determined after placing it on the designed meandered conductive loop. The loading of magnetic test sample on the meandered conductive loop of the split ring resonator perturbs the magnetic field concentrated on it thereby changing the resonant frequency of the sensor, which is recorded for the determination of permeability. The proposed dual band RF sensor is designed using the full wave electromagnetic solver. The equivalent circuit model and the corresponding numerical model of the proposed dual band sensor are discussed. The designed sensor is fabricated using the standard microstrip technology. The resonant frequencies of the proposed sensor are measured using the vector network analyzer (VNA), and are found to be 1.71 GHz and 2.35 GHz corresponding to 3G and 4G bands, respectively. Various standard materials are measured and the relative permeability is estimated using the proposed sensor in combination with the developed numerical model. The measured data are compared with values available in literature, and the typical error is found to be less than 8% for all the samples.