Slotted waveguide directional coupler characteristics

A moment method (MoM) solution for slotted waveguide directional couplers which is sufficiently accurate for predicting the couplers´ characteristics is demonstrated. The slot length in the waveguide directional couplers considered is about four wavelengths and the wall thickness is about 0.27 λ. To simplify the numerical computation, the formulation assumes a uniform field across the slot aperture and utilizes Galerkin´s method with the entire domain sinusoidal basis. A self-consistent method taking the finite wall thickness into account avoids an additional matrix equation, as in other MoM formulations. The final solution forms the basis for an efficient computer code applicable to dielectric-loaded slotted waveguide directional couplers. The uniform field assumption restricts the present solution to narrow slots. Numerical results verify, by comparisons with published analytical and experimental data, that this solution is valid for slot lengths as long as 4λ. A detailed discussion of the characteristics of narrow-wall and broad-wall slotted waveguide directional couplers is presented