Non-linearity of Soil Dielectric Constant as a Function of Radar Frequency and Soil Moisture Content

Soil is a mixture of four components: air, free water, bound water and soil particles. The microwave dielectric constant of soil is strongly dependent on the soil moisture content. The dielectric constant is a measure of the response of a material to an applied electric field, such as an electromagnetic wave. It has a real and an imaginary component. Soil particles’ dielectric constant depends on the physical properties of the soil, and not on frequency. Water’s dielectric constant depends on frequency, temperature and salinity and therefore so does the soil mixture's dielectric constant. There are different dielectric mixing models that are used to determine the dielectric constant or the moisture content. In this work, the concept of complex dielectric constant and its nonlinearity due to changes in frequency, and actual soil moisture values are revisited. The complex dielectric constant nonlinearity as a function of frequency for an example of clay soil is verified with a previously published work in the range of our Ground Penetrating Radar (GPR) bandwidth frequencies whose center frequency is at 1.5 GHz. The soil’s dielectric constant dependence on the soil moisture content will also be shown.