A four-element microstrip active patch array with beam scanning is described consisting of locked patch oscillators with DC bias phase control. The radiating elements are formed by transistor oscillators whose frequency is controlled by a rectangular patch. The oscillators are locked to an external source. Control of the radiated phase is achieved by varying the bias on the transistor. Close to 360° of radiated phase control can be achieved from each element by locating two oscillators on each patch. Measured results indicate that beam scanning in excess of 40° can be achieved.