Variation of complex permittivity of soils with moisture content using VNA

Abstract

The complex dielectric permittivity (∈′, ∈″) of sand (Kukas region field, Jaipur District, Rajasthan) and sandy loam soil (Sayla, Surendranagar District field, Gujarat) was measured in the frequency range from 100 MHz to 1.5 GHz, for various moisture contents in the soils, using a Vector Network Analyzer (VNA). It has been observed that, the dielectric constant and dielectric loss of the dry soils remain almost constant over this frequency range. The dielectric constant and dielectric loss increase with increase in moisture content in the soil, at any fixed frequency in this frequency region. At given moisture content in the soil, the dielectric constant of the soils decreases slowly with increase in frequency up to 1.5 GHz, whereas the dielectric loss of the soils decreases rapidly with increase in frequency up to 0.5 GHz, after which it decreases slowly with increase in frequency up to 1.5 GHz.