Offset-fed Slotted Antenna Practically Loaded with Split Ring as Water Quality Sensor for XBand Industrial Applications

This article describes the design, testing, and analysis of an offset-fed split ring-loaded slotted antenna for various water quality sensors. The antenna is designed to resonate at 10 GHz on a low-cost FR-4 substrate of dimensions 0.621 lambda(o)x0.467 lambda(o)x0.053 lambda(o) , where lambda(o) is the free space wavelength at the resonant frequency. The fabricated antenna finds excellent agreement with the measured antenna parameters. At 10 GHz, the antenna achieves a gain of 7.61 dBi, a nearly unidirectional radiation pattern, and a radiation efficiency of 76%. The research is further explored to use the antenna as a water sample sensor. The antenna is tested on various water samples by submerging it in them, and in the second scenario, contactless measurements at 10 mm away from the container's upper water level. The work examines the quality of the water by observing the shift in the resonant frequency (f(r)), the antenna quality factor with different total dissolved solvents (TDS) in the water samples, and changes in the reflection coefficient (S-11) values. It is observed that the antenna shows less than 1.5% numerical sensitivity (NS) with f(r), and high NS with the S-11. The antenna's S 11 and bandwidth vary and depending on the water sample. This antenna is suitable for Xband industrial and microwave laboratory applications.