Rigorous Full Wave Research Articles

Numerical techniques for planar and quasi-planar millimeter-wave passive components

The necessity for accurate characterizations of microwave circuits and components is well recognized. This is because of the use of higher frequencies and more complicated circuit configurations. This paper reviews two important numerical approaches to the analysis and design of printed circuit transmission lines, the planar circuit approach and the transverse resonance technique. The former is applicable basically to microstrip quasi-TEM circuits, and constitutes a considerable improvement compared to the conventional transmission line approach. It is, however, an approximate technique that cannot be expected to give extremely accurate results in all practical cases, particularly in the higher frequency spectrum. On the contrary, the transverse resonance technique, in a formulation generalized with respect to the conventional transverse resonance method, is a rigorous full wave technique that can be applied to the characterization of both planar and quasi-planar transmission lines. The extension of this method to the modeling of discontinuities is also illustrated.

Full wave theory and controlled optical experiments for enhanced scattering and depolarization by random rough surfaces

Controlled laboratory experiments afford an indispensable tool in the validation of the numerous theories on electromagnetic scattering and depolarization. In a recent article in Optics Communications [61 (1987) 91], a group at Imperial College reported some very stimulating observations on enhanced backscatter from rough surfaces with large mean square slopes. A second order iterative solution based on the rigorous full wave approximation indicates that contrary to the suggestions made by the researchers at Imperial College (based on their consideration of many other theories), the observed enhanced backscatter can be attributed to single scatter rather than multiple scatter.

Vertically polarized waves in inhomogeneous media with critical coupling regions, energy conservation, and reciprocity relationships

Using a generalized WKB approach rigorous full wave solutions are derived for the electromagnetic fields for vertically polarized waves propagating through inhomogeneous dielectric media with critical coupling regions. Both the real and imaginary parts of the permittivity profile are assumed to vary in the horizontally stratified media. The generalized WKB solutions are consistent with energy conservation and reciprocity relationships in electromagnetic theory. The reflection and transmission coefficients and the related characteristic surface impedance for inhomogeneous layers of finite thickness are computed as functions of the transverse wave number for several permittivity profiles. Excitation of propagating and evanescent waves are considered. For the trapped waveguide modes of the inhomogeneous layer the reciprocal of the reflection coefficient vanishes and the layer is characterized by a surface impedance. Some special permittivity profiles for which closed form analytic solutions of the electromagnetic fields are known are also considered. Computations derived from these closed form solutions are shown to be in good agreement with computations based on the generalized WKB solutions.