Generalized scattering matrix computation of the transition: microstrip line-rectangular waveguide, as a building block for the analysis of multilayer microstrip circuits and antennas

The coupling between a microstrip line and a rectangular aperture on its ground plane, plays and important role in the design of planar microwave circuits and antennas, including aperture-coupled microstrip lines, multilayer printed antennas and arrays. In previous works the transition microstrip line-aperture was used as building block, but it was only represented by an equivalent admittance. Also, the aperture coupled microstrip lines were represented by a 2/spl times/2 scattering matrix, but there is not a general matrix representation for the transition microstrip line-aperture. The computation of the generalized scattering matrix (GSM) for the transition microstrip line-rectangular waveguide is presented. This GSM is used as a building block for the analysis of multilayer printed structures. It can be cascaded with the same but opposed GSM to obtain the scattering matrix of aperture-coupled microstrip lines. Also can be cascaded with other GSMs to analyse different structures, such as a printed slot antenna and aperture coupled microstrip arrays.