Calibration block for digital beam forming antenna

A digital beam forming (DBF) antenna gives the possibility of obtaining precise control of the array transfer function starting at the individual array elements. The DBF has the advantage of flexible operation which can not be achieved with traditional beam formers. The onboard self-calibration circuitry is crucial to obtain precise pattern control (low sidelobes, high resolution, etc.). The paper describes a circuit which is used as a calibration loop in a DBF antenna.