RAY-OPTICAL METHODS FOR MODES IN GUIDING AND RADIATING STRUCTURES,
Abstract
The report describes natural modes in guiding structures by ray methods either from direct solution of the eiconal and transport equations of geometrical optics subject to asymptotic boundary conditions or from a modal consistency relation for sets of ray congruences. The applications are for general two-dimensional separable waveguides filled with a homogeneous or an inhomogeneous dielectric, and having boundary walls which are specified either by a variable surface impedance or which provide access to another dielectric medium. For non-uniform and curved waveguides, modal caustics play a key role in specifying the modal ray structure. Caustics of two classes which transform smoothly from one to the other with increasing frequency are exhibited and are specified as belonging either to tunneling or to whispering gallery modes. In addition, waveguides are treated where there is coupling between multiple ray pairs (as for example in a compressible plasma where electromagnetic and electroacoustic wave species exist). The treatment is extended to leaky waveguide structures and leakage coefficients are determined by modified ray methods. Finally, techniques are developed which allow an approximate modal description for a class of non-separable tapered waveguides. These utilize an analytic method which incorporates local separability and a method in which each region is approximated by a sectoral waveguide. Modal caustics are derived and the results from the two methods are compared. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1968
- Accession Number
- AD0685765
Entities
People
- Leopold B. Felsen
- Stewart J. Maurer
Organizations
- New York University Tandon School of Engineering