A microstrip Antenna for Underground Applications with Frequency Insenitivity to soil moisture variations

In this article, we propose a novel design of a buried rectangular patch antenna utilizing the ferromag-netic properties to ensure the resonant frequency resistivity against uctuations in soil permittivity,notably due to variations in its water content. The study initially prioritized determining the idealposition of the ferrite core introduced into the substrate and optimizing the external magnetic eldbias for its application. Subsequently, attention was directed towards evaluating the return loss of thedesigned antenna through simulation under conditions where humidity varies between 0 and 50%. Theresults indicated that the transmitter operates in two di erent modes: ordinary and extraordinary,with the latter maintaining a stable frequency with a deviation rate from the initial one on dry soilnot exceeding 3%, instead of the 50% observed for the former mode. This feature grants it the abilityto be deployable in applications with underground nodes, such as in the case of precision agriculture,without needing to intervene to adjust the operating frequency.