A transmission line model for microstrip configurations, for which separation of variables is possible, is presented. For this, the patch is modelled as a transmission line joining the radiating apertures. Each section of the transmission line is replaced by a π-network. The effect of apertures in the direction perpendicular to the direction of propagation is included through the complex eigenvalues. The effect of mutual coupling between the radiating edges can be described using variational technique and finally incorporated in the equivalent circuit of the structure. Application of the transmission line method appears to be large. Some patch shapes have been analysed and others indicated.