A microstrip antenna has a single dielectric layer with a conductive ground plane disposed on one side, and an array of spaced apart radiating patches disposed on the other side of the dielectric layer. The radiating patches are interconnected with a feed terminal via stripline elements. Responsive to electromagnetic energy, a high-order standing wave is induced in the antenna and a directed beam is transmitted from and/or received into the antenna. A dual­-mode embodiment is configured such that standing wave nodes occur at the intersection of orthogonally situated striplines to minimize cross-polarization levels of the signals and the cross-talk between the two modes of operation.