Abstract: A beam forming device that enables the use for wideband digital beam forming and provide a high accuracy a beam forming device comprises a transmitter arrangement and a receiver arrangement, wherein the total number of transmit antennas and receive antennas is at least three. A beam forming unit performs beam forming to obtain beam formed output signals from said receive signals by use of corrected beam forming weights. A correction unit corrects preliminary beam forming weights in amplitude and/or phase by use of frequency-dependent final calibration coefficients representing the different amplitude and/or phase responses of the different channels between said at least one transmit antenna and said at least one receive antenna at two or more separate frequencies covered by the radiation transmitted towards the scene.