Microwave dielectric properties of materials

Abstract

Dielectric properties of natural media at microwave frequencies have been reviewed, and the effects of various physical parameters to the behavior of their permittivity have been discussed. Since most natural media are heterogeneous, theoretical derivation of their dielectric properties is not straightforward. Measurements provide useful information for model development and evaluation, but only within the range of the covered physical characteristics and employed frequencies. The permittivity of pure and saline water is the key to modeling the behavior of most natural media; gaps still occur for its values at nearfreezing temperatures, especially at high microwave frequencies. More experimental data are needed to confirm the behavior of wet snow at frequencies above 18 GHz. Measurements of the permittivity of sea ice for various salinities and ice types, especially for high brine volumes and at temperatures above -5 ¼C, would substantially benefit modeling of the behavior of sea ice. Permittivity measurements of various types of vegetation are needed to test presently available semiempirical models and further develop them.