Overlaid parallel coupled inset dielectric guides for broadband applications to directional couplers

Overlaid parallel coupled inset dielectric guides are proposed for broadband applications to directional couplers, and analyzed by using the integral equation formulation and Galerkin's procedure. Results are presented to illustrate effects of thickness and dielectric constant of the overlay on propagation and coupling characteristics. It is found that by suitable choice of these parameters very flat coupling can be achieved for a wide frequency range.