Stacked patches consist of one of more conducting patches which are parasitically coupled to a driven patch. This configuration overcomes the narrow bandwidth limitation by introducing additional resonances in the operating band, while maintaining the advantages of the conventional patch antenna. The elliptical-ring stacked patch antenna consists of two annular rings, each etched onto separate dielectric substrates, stacked on top of one another. The active element and its feed pin are incorporated in the bottom substrate with groundplane.
Impedance bandwidths up to 30% are achievable with this configuration, while circular polarization may be obtained by changing the geometries of the circular ring patch antenna to elliptical and offseting the feed point from the main axis....Typical radiation pattern at the center frequency Typical S11 performance of the antenna