Gw. Hanson et Ce. Baum, PERTURBATION FORMULA FOR THE NATURAL FREQUENCIES OF AN OBJECT IN THE PRESENCE OF A LAYERED MEDIUM, Electromagnetics, 18(4), 1998, pp. 333-351
It is well known that the natural frequencies of an object are importa
nt distinguishing features which can be used in target detection and d
iscrimination schemes. These natural frequencies are governed by the s
ize, shape, and material composition of the object, as well as the env
ironment in which the object resides. Since a given object of interest
may reside in many different environments, it is of interest to relat
e the natural frequencies of an object when in free-space to the natur
al frequencies of the same object when immersed in a non-homogeneous e
nvironment. In this paper a perturbation formula is developed which re
lates the free-space natural frequencies of an object to those of the
same object in the presence of a planarly layered medium. The perturba
tion formula is valid for intermediate spacing between the object and
the nearest planar interface. Numerical results are shown for the natu
ral frequencies of a wire in the presence of a layered medium.