Calibration of smart antennas in a GSM network

Smart antennas can achieve a considerable gain in spectral efficiency provided that errors due to mutual coupling and amplitude or phase errors of the antenna elements are negligible. Calibration by the knowledge of the directions of the wavefronts transmitted by a second base station lessens the influence of these imperfections. This study describes the calibration results of general planar antenna arrays in the existing GSM network of the German network operator Mannesmann Mobilfunk GmbH. The presented direction based calibration algorithm does not only take into account the multipath propagation of discrete wavefronts, but also the considerable angular spread. Such a procedure is possible when the base station is carrying operational traffic and is not limited to offline or even preinstallation calibration. A discussion gives some insights on how to obtain best calibration results.