A Magnetic Coupling-Based Technique for Buried Antenna’s Frequency Adjustment in Wet Soil

Wireless Underground Sensor Networks for precision agriculture applications consist of wirelessly connected underground sensor nodes that communicate through the soil. Thus, the resonant frequency of the buried antenna depends on the soil’s dielectric permittivity. In addition, the soil’s volumetric water content in nature can vary unpredictably due to the weather conditions and irrigation, causing permittivity fluctuations and hence, frequency instability of deployed antennas. In this paper, we propose an inductive coupling-based technique allowing the self-adjustment of the buried loop antenna’s resonant frequency subject to a wet soil environment.