In a method for calibrating at least two cross coupled antenna element groups in an antenna array, calibrating (S1) the antenna elements within each group of antenna elements. Further, in a respective calibration transceiver in each group, measuring (S2) a coupled signal within each group and a cross-coupled signal originating in another of the at least two groups. In addition, determining (S3) a respective relative phase and amplitude difference between said at least two groups based on the measured coupled signal and said cross-coupled signal, and determining (S4) the true phase and amplitude difference between the at least two groups based on the determined respective relative phase and amplitude differences. Finally, calibrating (S5) the at least two antenna groups based on the determined true phase and amplitude difference.