Effect of a cover layer on the edge admittance of a wide microstrip

The canonical problem of a grounded dielectric slab with a truncated upper conductor and a dielectric cover layer is solved by the Wiener-Hopf technique. The method yields the value of the reflection coefficient at the open edge and the equivalent edge admittance. Numerical results show that the presence of a cover layer increases both the conductance and the susceptance. An increase in the value of edge conductance corresponds to an increase in the radiated power and surface-wave power. An increase in the value of the susceptance corresponds to an increase in the fringing capacitance at the edge. This results in a reduction of the physical length of a resonant rectangular patch. On the basis of Wiener-Hopf analysis it is seen that the space-wave power and the power carried by the surface wave are separated from the total radiated power. The numerical results show that the radiation efficiency decreases with an increase in the cover layer thickness