Compact antenna based on split ring resonator as high Q-factor antenna for liquid permittivity measurements

Abstract

Abstract Microwave sensing is important to measure the permittivity of the materials or detecting a material. In this current work, a compact antenna for WLAN application with circular polarization is designed. We are supposed to use it as a sensor to determine the permittivity of industrial oil. For calibration of the sensor, the gasoline and petrol are utilized based on Debye theory and also butanol is checked. This antenna is designed based on Microstrip slot antenna with bent feed line and special split-ring resonator (SRR) as a metamaterial (MTM) element for 4 GHz, it is shown that metamaterial can be considered for improving the Q-factor and matching where the return loss is reduced from −16.5 to −33.5 dB and the Q-factor is increased from 2.39 to 32.9. It covers 4–5 GHz with the bidirectional pattern with gain of 4 dBi which makes it useful for putting inside of liquids. The total dimensions of this resonator are 20 × 20 × 1.6 mm and the FR-4 low-cost substrate is used and the experimental results are confirmed the simulations results by HFSS commercial full-wave software. In fact, this method can be used for fast detecting oil condition and longevity by checking the resonances’ shift and permittivity.