Planar and Open-Boundary Waveguides
The Electromagnetics Research Group has performed extensive analytical and experimental studies on modern planar and open-boundary waveguides. Contemporary communication systems make extensive use of electronic components based on printed-circuit boards, integrated circuits, fiber optics and integrated optics. The interconnections among devices in such circuits is by wave guiding structures which are usually planar and/or open. Typical of such waveguides are PC board traces, stripline, microstrip, optical fibers and integrated dielectric waveguides. A property common to all these structures is that they are in some sense open, and can consequently lose energy to the surrounding environment. The characteristics of this class of guiding structures are significantly more diverse and complex than those of more traditional closed waveguides.
Except for several canonical structures, this class of waveguides leads to inseparable boundary conditions which render conventional differential-operator methods ineffective. Integral-operator formulations become necessary and the analysis becomes relatively complex. The guiding region is usually immersed in a layered background environment (e.g., conductor/ substrate/cover for microstrip) and the necessary Green's function kernel for the integral operator must be expressed in Sommerfeld-type integral representation. Properties of the latter Green's function have a strong influence on the propagation-mode spectrum of the waveguide structure.
Unlike closed waveguides for which the propagation modes are discrete and infinite in number, open structures support a propagation-mode spectrum consisting of a finite number of discrete modes augmented by a continuous spectrum. Some discrete modes of the open guides can be leaky and lose energy to the surrounding environment. The continuous spectrum for integrated conducting or dielectric open guides has not been adequately understood until very recently.
Efforts at the The Electromagnetics Research Group have been devoted to understanding the propagation-mode spectrum of integrated open waveguides. Contributions include the first unambiguous conceptualization for the continuous spectrum and the categorization of various proper and leaky discrete modes based upon properties of the Green's function kernel. The excitation of proper discrete modes and their scattering by device discontinuities in interconnected circuits has also been investigated. These efforts are continuing and are expected to lead to the discovery and understanding of fundamental new wave phenomena.
