The invention is directed to a dual-frequency stacked patch antenna. In one embodiment, the antenna comprises a pair of electrically conductive, nested, tub-like structures and a feed surface. The edges of the tub-like structures and the feed surface define a surface that is adapted to be conformal to an application surface that defines a cavity in which the antenna is positioned. The edges of the tub-like structures and the edge of the feed surface define a pair of slots for receiving and/or transmitting two signals with different center frequencies. Located and extending throughout each of the slots is a slot modification structure comprised of inter-digitated fingers that provide capacitive loading and enhance the low observability of the antenna.