UWB in-situ soil permittivity probe with a novel iterative permittivity calibration method

A novel coaxial probe is developed for measuring complex permittivity of soils in-situ from 10 to 1000 MHz without taking soil samples. The dielectric constant and conductivity of soil is derived from step-frequency reflection taken inside a small freshly bored hole. As a result, permittivity at various depths with in-situ moisture content and soil texture can be obtained in the fields. A novel permittivity calibration method was developed to account for the frequency- and material-dependent geometrical factor which causes bias errors in conventional calibration methods. Simulated and experimental data are presented to prove the accuracy and efficiency of the proposed probe and calibration method.