A switched loop RF radiator circuit, comprising a radiator element, a RF input/output (I/O) port, and a balun coupled between the radiator element and the (I/O) port. The balun includes a 180.degree. switched loop circuit having transmission line legs coupled to a balun transition to provide a selectable phase shift, and a microelectromechanically machined (MEM) switch Many radiator circuits can be deployed in an electronically scanned antenna array.