This patch array does not use a traditional feed network, but provides a nice practical way to achieve the higher gain and bandwidth that is possible with patch arrays without the need for an often sensitive and hard-to-design feed.
The 2x2 stacked patch is suitable for numerous microwave and millimeter wave applications such as tracking and search radars, altimeters, remote sensing, terrestrial and aerospace communication systems.
A general problem with patch arrays is spurious radiation caused by feed networks. There are different ways to reduce spurious radiation but generally these require feed mechanisms that are difficult to manufacture. An advantage of the 2x2 stacked patch is that it uses a simple feed - a single feed line from below the ground plane excites the feed patch which in turn couples to the upper patch array. This results in minimal spurious radiation while maintaining a good bandwidth and gain....Transparent view of the Stacked patch array model.