S-parameter description of microstrip slot-couplers

A method for the analysis of slot-coupled microstrip lines is presented. Expressions derived for the equivalent circuit impedances in terms of modal field expansions permit 5-parameters to be computed directly. Moreover, the derived 5-parameter expressions show a stationary nature with respect to the induced slot field. Preliminary measurements are in good agreement with theoretical predictions from 0.5 GHz to 18.0 GHz. Efficient computation and results which can be incorporated with existing CAD programs are advantages offered by this technique.