Analysis on the standing wave method in free space using spectral domain approach

The standing wave method for the spherical wave incidence has been developed to estimate the complex permittivity of construction materials. In this paper, the behavior of spherically standing wave in front of the construction materials has been theoretically analyzed by the use of the spectral domain approach. As a result, the relationship between the complex permittivity and the reflection coefficient at the front surface of the grounded materials is derived, when a spherical wave is irradiated toward the material. This relationship can be expanded for all types of the incident wave including the plane wave incidence. A number of the numerical models for the composite materials have been so simulated by means of the FDTD technique as to check the validity of the relationship.