THEORY OF MULTI-HOLE AND MULTI-SLIT DIRECTIONAL COUPLERS.

A new design theory for multi-hole and multi-slit directional couplers is presented. The VSWR and directivity of a coupler can be obtained from the theory. S-matrix representation of one coupling hole is the basis of the formulation. The S-matrix is decomposed into two F-matrices in accordance with the even and odd excitations. Application of this idea to n coupling holes gives the overall S-matrix. Using the theory, the design parameters of couplers are derived which gives a VSWR of 1 and infinite directivity at the center frequency. The theory can be applied to design frequency separation filters used in microwave and millimeter-wave communications systems.