Coaxial Line Measurement and Analysis of Electromagnetic Properties of Soils for Sensor Applications

We report complex permittivity, conductivity, magnetic susceptibility, and attenuation for soils collected from a typical site in a current theater of operations. Our experimental setup consists of three network analyzers along with custom-built sample holders and data reduction and analysis software. The sample holder has the advantage of large sample volume and a resulting higher signal to noise ratio. This system was developed to determine the electrical properties of soils over a wide frequency range from 100 Hz to 8 GHz. The lower frequencies are applicable to capacitive sensors for small shallow targets, while the higher frequencies are applicable to ground-penetrating radar (GPR) from 50 MHz to 2 GHz and beyond. S-parameter data is collected and reduced using a method, initially developed by Nicolson and Ross (1970)(1), for the determination of dielectric permittivity, magnetic permeability, and loss tangent from measured S-parameter data. Experimental results are compared with site geology and mineralogy. Applications include detection of tunnels, land mines, unexploded ordinance (UXO), concrete reinforcements, and other shallow compact targets.