| All dielectric materials, by nature, exhibit a frequency dependent permittivity. This property, termed dispersion, must be taken into account when materials are employed in applications that span very broad frequency ranges; such as broadband antenna applications and the design of Low Observable structures. Therefore, an accurate and compact representation of this frequency dependence over very broad bands of frequencies is needed. In addition, Time Domain Computational Electromagnetics computer codes will only realize their full potential when such a representation is used for modeling of material bodies, since only then will the pulse solution truly contain the proper solutions for the full spectrum of the pulse. In this paper such a representation is developed. It is shown that the analytic function properties of the permittivity lead to a special set of basis functions with which the behavior of any physically realizable dielectric can be analyzed. Because of this analyticity, data obtained over convenient portions of the Radio Frequency spectrum can be continued into other portions of the spectrum where measurements may be more difficult to perform. Two analysis and one design problem are used to illustrate the application of the method. |
