English abstract
This research presents a novel soil moisture measurement technique utilizing a 1.4 GHz
microstrip antenna, addressing the critical need for efficient water management in the context of
global food production.
The method investigates the impact of varying soil moisture levels on the antenna's resonant
frequency and reflection coefficient (S11) using near field properties from a low-profile antenna.
By capitalizing on the antenna's sensitivity to the surrounding medium's dielectric constant,
introducing an indirect and non-invasive approach to estimate qualitatively the percentage shift of
near field sensor.
Both simulations on loam soil and empirical tests on sandy loam soil consistently reveal a
downshift in resonant frequency with increasing moisture levels. For instance, in 10 mm deep
loam soil, the resonant frequency decreases from 1.32 GHz to 1.195 GHz as moisture content
rises from 5% to 20%, with similar trends observed at greater depths. The reflection coefficient
S11 also increases in wetter soils, indicating a high impedance mismatch. Empirical data from 10
mm deep sandy loam soil corroborates these findings, with a resonant frequency decrease from
1.408 GHz at 5% moisture to 1.345 GHz at 20% moisture.
These results highlight the potential of resonant frequency shift as a reliable indicator of soil
moisture, offering a valuable tool for precision agriculture and sustainable water management
across multiple sectors.
