In this communication, based on spectral domain immittance (SDI) matrix approach, Green's function for multilayered structure is derived and the closed form expression for radiation characteristics are obtained in terms of the electric surface current density. For a rectangular patch, its current distribution is approximated by transmission line model that enables one to evaluate the radiation characteristics of the radiating element. Numerical results based on this formulation are presented indicating that gain of an antenna can be enhanced if parameters are appropriately selected. Graphs of relevant parameters are presented enabling the designers to see clearly that with an appropriate superstrate permittivity and spacing between the cover and the radiating element can narrow the beamwidth and enhance the antenna gain. The procedure described is quite general and can be applied to other printed structures. The formulation as well as numerical computation both are simple and easier than other analyses.