An antenna for communicating with mobile devices in a land-based cellular communication system via an antenna beam having a width, azimuth angle and downtilt angle. The antenna includes: a two dimensional array of radiating elements (31-34); and a feed network (35-39) from a feed line to the radiating elements. The feed network includes: downtilt phase shifting means (35,36) for varying the phase of signals supplied to or received from the radiating elements so as to vary the downtilt angle of the antenna beam; azimuth phase shifting (38,39) means for varying the phase of signals supplied to or received from the radiating elements so as to vary the azimuth angle of the antenna beam; and beam width adjustment means (37) for varying the power or phase of signals supplied to or received from the radiating elements so as to vary the width of the antenna beam.