Compact Wideband Circularly Polarized SRR Loaded Slot Antenna for Soil Moisture Sensor Application

Abstract

– This paper presents a coplanar waveguide (CPW) fed corner truncated square slot antenna loaded with a split ring resonator (SRR) for soil moisture sensor application. The truncated corner square slot produces a circularly polarized wave with two orthogonal degenerate modes at 4.12 GHz with 3-dB axial ratio bandwidth of 17.69%. Further, the axial ratio bandwidth is increased to 21.81% by loading a rotated SRR on the slot. The split gap of the inner ring of SRR is rotated 90° with respect to outer ring gives circular polarization (CP) at 4.62 GHz. The wideband CP performance is achieved by the combination of truncated corner slot and rotated SRR mode resonances. Both bands are tuned independently to optimize the wide axial ratio bandwidth. The designed antenna is fabricated, and its performance is verified experimentally. The measured impedance bandwidth of 2.53 GHz (61.40%) and axial ratio bandwidth of 0.9 GHz (21.68%) with a peak gain of 2.74 dB is observed. The proposed wideband CP antenna is utilized for soil moisture sensing application and high sensitive microwave sensing application. © 2020