Multi-frequency characteristics of unequal element spacing array antenna for mobile base station use

In mobile base station antennas, linear array antennas are employed to achieve shaped beams in the vertical plane. Also, antennas are designed to achieve multi-frequency use. In the case of expanding multi-frequency range, conventional equal element spacing configuration shows a defect of producing grating lobes. In order to suppress grating lobes, unequal element spacing is promising. In this paper, a radiation pattern synthesis based on a least mean square method (LMS) is applied to unequally spaced array configurations. In frequencies of 900 MHz, 1.5 GHz, 2.0 GHz, and 2.5 GHz, calculated results are presented. Suppression of grating lobes and increase of antenna gain are shown. Also, simulation results by FEKO using electric point source and dipole as array elements are shown to confirm accuracy of this method.