Electromagnetic coupling between curved dielectric waveguides

An analytical method for coupling characteristics of curved dielectic waveguides is presented. We express a total coupled field around the coupling mechanism by linear combination of mode fields of individual curved guide with waght function mi(z) (i=1,2). Loentz´s theorem and divergence theorem are applied to two sets of field combination, i.e. the total coupled field and individual guided-mode fields. Then, we obtain a coupled mode equation for weight functions in which the coupling coefficients vary along the coupling mechanism. As numerical example of the theoy, two types of coupling mechanism are considered, i.e. the structure of Whispering Gallery (W.G.) mode coupling in two circular dielectric disks, and that of WG. mode on the disk and dominant mode on a rectangular dielectric waveguide. Coupling coefficients, coupled power and electric field distribution around the coupling region are numerically obtained. Mesurement result of electric field distribution around the coupling region, on 24 GHz band, is also presented.