Metamaterial based a printed monopole antenna for sensing applications

The applications of metamaterials (MTM) based on interdigital capacitor (C-int) and via that extends the function of conventional printed antennas to encompass passive wireless sensor at microwave frequencies is presented in this article. The proposed antenna consists of two rectangular arms of C-int connected to a printed microstrip monopole with six shorting via wires soldered to the ground plane. The size of the whole antenna structure, including the proposed MTM, is found to be less than 0.45 at 1.35GHz. The antenna performances, in terms of return losses (S-11), bandwidth (BW), gain (G(o)), and radiation patterns, are measured in the free space environments. To characterize the sensing properties, the antenna performance is tested in close to different types of water. It is found that the antenna exhibits a significant change in the S-11 spectra relatively to the water introduction. These advancements in the performance of the antenna are believed due to the MTM structures. The antenna shows excellent matching over several bands, however, only the resonance mode at 1.35GHz, which the gain is relatively high, is used for sensing. The sensing mechanism is based on the S-11 spectrum change.