Dielectric Properties of Beans at Ultra-Wide Band Frequencies

Dielectric properties of three varieties of common beans (Phaseolus vulgaris L.) were determined at Ultra-Wideband (UWB) frequencies (3–10.6 GHz) using a free space transmission method. Beans were conditioned to get different moisture contents; the bulk density of beans (ρ) increased at higher moisture contents. Permittivity and conductivity of beans also increased with moisture content. The dielectric constant (ε’) remained practically constant in the studied frequency range, while loss factor (ε’) decreased in frequency. The ε’/ρ vs ε’/ρ complex-plane plot (Argand diagram) was built and a linear trend was observed, with positive slope. However, this slope value decreased at higher frequencies.