A modified microstrip ring resonator sensor with lumped element modeling for soil moisture and dielectric predictions measurement

This paper proposes a modified microstrip ring resonator sensor with four-legged element structure design for microwave soil aquametry application. Dielectric prediction based on different moisture content, m.c.   for measurement of peat and sand soils by applying conversion of the measured reflection coefficient, |Γ| to relative dielectric constant, εr′ is computed via a proposed lumped element model. The microstrip ring resonator sensor is designed to operate between 0.5 GHz and 4.5 GHz with the resonance at 3.2 GHz. In this work, this model was found to be accurate with an error within 5% in dielectric prediction with the commercial dielectric probe for peat soil (⩾28% m.c.) and sand soil (⩾10% m.c.). For soil moisture content prediction, the mean deviation between predicted and actual moisture content is within 1.5% m.c. for both peat and sand soils in the experiment.