A technique in which an antenna array, with individual phase control for each antenna, is used to produce or receive a highly directional radio beam. For radar it provides a way of steering or scanning the beam at high speed without any moving parts. Wireless routers and devices using the latest protocols can use similar techniques to adaptively focus the wireless signal along the best path between the router and devices, rather than using a wide-angle broadcast that wastes energy. See also multiple-in, multiple-out.