According to another embodiment, a phased array antenna system comprises a plurality of stacked-patch microstrip antenna elements arranged in a two-dimensional array, each stacked-patch microstrip antenna element of the plurality of stacked-patch microstrip antenna elements including a pair of conductive patches disposed above a ground plane on a dielectric substrate, wherein the dielectric substrate of corner stacked-patch microstrip antenna elements in the array has a dielectric constant lower than a dielectric constant of the dielectric substrate of non-corner stacked-patch microstrip antenna elements in the array.

In one example, the dielectric substrate of the corner stacked-patch microstrip antenna elements in the array has a density lower than a density of the dielectric substrate of the non-corner stacked-patch microstrip antenna elements in the array. In one example, the dielectric substrate of the corner stacked-patch microstrip antenna elements in the array includes a plurality of cavities arranged in a regular pattern laterally across the dielectric substrate. In another example, the sizes of the plurality of cavities decrease outwardly from a center of the dielectric substrate.

In another example, the dielectric substrate is a multi-layer dielectric substrate, and wherein the pair of conductive patches includes a top patch disposed on a first surface of the multi-layer dielectric substrate and a bottom patch aligned with the top patch and disposed within the multi-layer dielectric substrate between the top patch and the ground plane.