Design of a two-layer, capacitively coupled, microstrip patch antenna element for broadband applications

A broadband, contiguous stacked, two-layer, square microstrip patch antenna element design is described which can be used for linear or circular polarization. Single layer microstrip patch theory for the rectangular patch radiator is presented and used as a basis for understanding the two-layer patch configuration. The theory is modified to predict radiation patterns and resonant frequencies of the two-layer microstrip patch antenna element. Experimental results include the radiation patterns, dominant resonant frequencies (TM1 0 mode), return loss (S11 ), and bandwidth for X band elements as a function of dielectric constants, dielectric thicknesses, and patch sizes.