A Different Method Determining Dielectric Constant of Soil and Its FDTD Simulation

Ercan Yaldiz,Mehmet Bayrak

doi:10.3390/mca8030303

Abstract

In this study, a different method determining the dielectric constant of soil via probes is presented. The method is based on the principle of measuring pulse delay in a given matter. The experimental study, which was carried out basically using an HP8753A vector network analyser, was repeated for various soil mixtures having different values of wetness. The results obtained from the measurements have clearly shown that the dielectric constant of the soil was increasing almost proportionally with that of the moisture content in the soil. The suitability of the measuring method was also checked with a number of simulation results obtained directly using the finite difference time domain method (FDTD).

Highlights

The dielectric constant is defined as the relative permittivity of a given material
A lot of researches have been carried out so far concerning the dielectric constant of the soil and the results shown that the electromagnetic radiation was both delayed and attenuated in soil, depending on the frequency and the moisture rate in the soil
While the relative dielectric constant of water was found to be about 80 in lower microwave frequencies, the measured values of relative dielectric constant for different soil compositions are reported to vary between 4-40

Summary

Its FDTD Simulation

Since equation (6) is valid for electromagnetic waves propagating in any given medium, the dielectric constant for that medium can be determined by measuring the transmission delay of the wave. Holding the two coaxial probes in the air I distance apart and measuring the pulse delay fa' the velocity of the electromagnetic wave c can be. Vs and fs represent the velocity of electromagnetic wave and pulse delay time respectively in a given soil mixture. Where Cs and f.1s parameters represent the relative dielectric constant and the relative magnetic permeability respectively in given soil mixture. Ca = 1 and f.1a = 1 represent the relative dielectric constant and the relative magnetic permeability respectively in the air. Assuming the distance I between the two probes are variable, the relative dielectric constant Cs can be calculated in this case in terms of pulse delay fl, (by remembering fa = lie) as follows; GS=(cf:r. The simplicity of the measuring set up enabling to get the reliable results in short time may be regarded as the main advantage of the proposed method

Sample Pool

The relative dielectric constant