Dual and triple band stacked patch antennas with U-slots

Recently, it was shown in [1] that, by cutting one or two U-slots on the patch of an L-probe fed patch antenna, dual or triple band characteristics can be obtained. This example turns out to be a specific case of a general technique of designing dual and triple band patch antennas: namely, if one cuts U-slots in the patches of a broadband patch antenna, band notches will be introduced and the broadband antenna becomes a multi-band antenna. In this paper, we apply this technique to coaxial fed and aperture coupled stacked patch antennas.