H-Slot Sensing Antenna System for Termites Detection

In this article, a novel H-slot antenna system is presented for combating termites. Considering the effect of the moisture content (MC) in the presence of termites, a noninvasive technique that is based on detecting the moist spots of wood is introduced. The proposed sensing antenna system consists of two identical microstrip-fed H-slot antennas and a reflector at a distance of 1 cm. Based on the transmission coefficient level between the antennas, the moisture within the wood is detected. By utilizing the reflector, the system can achieve multiband operation and enhance the simulated gain to approximately 8.76 dBi, thereby improving its detection capability. The proposed single antenna was built on a commercial low-cost Flame Retardant 4 (FR4) substrate with compact dimensions of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$20\times 20\times 1.6$ </tex-math></inline-formula> mm. Through optimization of the stub dimensions, the proposed antenna resonates effectively at 4.2 GHz. The simulation results demonstrate that the system can achieve excellent moisture sensing capabilities not only across the wood surface but also to a depth of 0.95 in using a perfect electric conductor (PEC) reflector. Regardless of the wood type, the proposed sensor can also identify moisture levels of 30%. The complete sensing system has been manufactured, and the simulation results have been validated through measurements, confirming the efficiency of the proposed system as a moisture sensor for wooden structures.