WAVE SCATTERING FROM SLIT COUPLED CYLINDRICAL CAVITIES WITH INTERIOR LOADING .1. FORMULATION BY RAY-MODE PARAMETRIZATION

Aperture-coupled enclosures with low internal losses and low radiation damping give rise to prominent features in the plane wave scattering behavior that can be tied to the internal resonances. When the interior is loaded with layers of boundaries that confine the accessible region to the vicinity of the enclosing surface, thereby simulating a peripheral waveguide, the interior wave phenomena can be modeled in terms of guided modes; the exterior wave phenomena, at high enough frequencies, can be modeled in terms of the ray fields of the (conventional or uniformized) geometrical theory of diffraction (GTD). Coupling between these alternative parametrizations is accomplished by the aperture. A self-consistent system structure involving state vectors for wave amplitudes, coupling matrices at scattering centers, propagator matrices between scattering centers, etc., can be constructed to describe the scattered field parametrized in this manner. In a two-part sequence, this strategy is applied here to a test geometry comprising a perfectly conducting smoothly convex cylindrical thin outer shell perforated by a narrow axial slit; the slit grants access to an interior loaded with a smoothly convex perfectly conducting cylinder so as to form a peripheral guiding region of moderate width, with variable cross section and without special symmetries. Special attention is given to reduced forms that emphasize, respectively, operation away from, or near, an internal resonance. The resulting formulations in these different regimes, contained in Part I, may be regarded as regular and anomalous modifications, respectively, of smooth cylinder GTD, caused by high-Q cavity coupling. The anomalous near-resonance case is treated in detail in Part II, together with a numerical example.