Radiation pattern synthesis of an unequally spaced array antenna

The IMT 2000 mobile communication system uses the 2 GHz band so the base station antennas are expected to operate in the frequency band of the conventional systems (800 MHz, 1.5 GHz) and the new system (2 GHz). In the multi-frequency operation, an unequally spaced array antenna has the advantage of suppressing grating lobes produced in the higher frequency bands. This paper proposes a radiation pattern synthesis method for an unequally spaced array antenna. The LMS (least mean square) method is employed. As an initial study, the ability of designing low sidelobe patterns is shown. In order to improve the design accuracy, a matrix that enables weighting of the radiation pattern is introduced. Adequate value of weighting is studied and excellent low sidelobe patterns are achieved.