Enhancing the resolution in imaging using folded metamaterial split ring resonator structure at microwave frequencies

Abstract

A novel and better resolution topology for reducing the sensing area of conventional Split Ring Resonator (SRR) metamaterial structure is proposed. The conventional planar SRR structure is fabricated on a thin flexible film and is folded to raise its split region slightly up with respect to the plane of the SRR (Folded Split Ring Resonator-FSRR). The structure exhibits strong localization of electric field in the projected region of the sensor, by confining the evanescent waves in that region having dimension much smaller than the operating wavelength. The proposed sensor is placed between transmitting and receiving probes of a Vector Network Analyzer (VNA) to form the sensing probe. Two dielectric samples arranged at different distances of separation are scanned and the corresponding transmission characteristics S21 are drawn for analysing the image resolution. The resolution and sensitivity of the above proposed sensor is compared with conventional SRR and is found to be superior in performance. This novel FSRR provides a better resolution and thereby overcomes the diffraction limit in imaging up to λ/30, whereas for the conventional planar SRR it will be around λ /15. The design is simple, compact and inexpensive. The potential of proposed sensor can be extended to sub-wavelength imaging of dielectric materials, biological samples and can be used for non-destructive testing.