Controlling the polarization state of signals to be transmitted from a MIMO capable radio base station node to a plurality of user equipment, which radio base station node comprises a precoder unit connecting a first and a second virtual antenna port to a respective first and second transmit antenna port, by the steps of controlling (S10) a relative phase between transmitted signals from the first and second transmit antenna port to provide a predetermined pair of orthogonal polarization states for signals transmitted on the first and second virtual antenna ports, and interchanging (S20) the polarization states of the first and second virtual antenna ports, to provide transmitted polarized signals with alternating polarization states.