THEORY OF COUPLED WAVEGUIDES

Abstract

In this paper, the author endeavors to study the diffraction of electromagnetic wave by a long slot with conducting environment on opposite sides (i.e., a slot-coupled system of arbitrary shapes) from the viewpoint of coupled waves. A novel theory, which is justified by clear physical reasoning, is presented for a practical solution of the relevant boundary-value problem. In the light of this theory, problems of coupled waveguides, like problems of a single waveguide structure, are attacked by the same mathematical approach, namely, the theories of development in the orthogonal functions. Thus, two types of problems heretofore treated diferently are brought under a unified and coherent point of view. To illustrate the applicability of the present theory, the author solves the problem of a long slot directional coupler, whose usefulness in the development of long-distance waveguide transmission is well-known, and derives a set of original formulas for computing the coupler parameters. As concluding remarks, some further appliations of the theory are freely discussed.