A circularly polarized array antenna (30) is disclosed. A single layer dielectric substrate (36) has a ground plane (32) located on its upper surface of the substrate and covering only part of the upper surface. A plurality of antenna elements (40-54) are also located on said upper surface of the substrate. Each antenna element has a slot element (60-74) formed in the ground plane and a respective loading element (80-94) located within each slot element. The antenna elements being arranged in a regular array where each respective slot element is sequentially rotated in space with respect to adjacent slot elements, and the loading elements generate a perturbation under excitation. A microstrip feed network (100) is located on the underside of the substrate to provide excitation to each slot element, and including feeds of different lengths to be electrically sequentially rotated in common with spatial rotation of the slot elements. A single microstrip feed point (108) extends to the edge of the substrate for connection purposes. A reflecting plane is located parallel to and spaced apart from the underside of the substrate. The ground plane extends to cover the entire microstrip feed array.