Experimental Characterization of the Effective Propagation Constant of Dense Random Media

In this paper, a new technique for measuring the effective propagation constant of dense random media is presented. This technique involves two major steps: 1) measurement of the mean bistatic scattered field of a cluster of the random medium confined in a spherical boundary and 2) characterization of the complex permittivity for a homogeneous dielectric sphere having identical radius and bistatic scattered field as those of the spherical cluster of the random medium. Using this measurement technique, not only the effective propagation constant of complex dense random media for which analytical solution does not exist can be characterized, but it can also be used to establish the validity region of the existing models. The sensitivity analyses of the proposed algorithm show that the imaginary part of the effective propagation constant can be measured very accurately. It is also shown that the effective complex permittivity of media with very low dielectric contrast or volume fractions can be characterized accurately. Measurements of the effective propagation constant of different dense random media comprised of homogeneous spherical particles of different packing densities are reported and compared with the existing analytical models.