Contents I. INTRODUCTION
Tilting the main beam below the horizon has often been requested to reduce the interferences in mobile systems, thus electrically adjustable antennas in base stations have been used widely in the mobile communication systems. There are usually two ways to realize beam tilting. One approach is changing the antenna's installation position directly, which requires a costly positioning system. The other method is changing the phase of current feeding antenna elements, commonly realized with a phased array using phase shifters. The commonly used phase shifters are PIN phase shifters and mechanical phase shifters. The former switches faster but is cost. The latter is lower cost, although it is slower to adjust the phase. There are some papers on electronic beam tilting of base station antennas [1] [2], however, few papers on the analysis of the electrically adjustable antenna array systematically, including the feed network, phase shifter and radiation pattern. In this paper, we use multi-port connection method to evaluate the system of electrically adjustable antenna array. The whole system is divided into several subsections, the scattering matrix for the whole network is obtained while the scattering matrix of each subnet are given. Then the currents on each antenna element are calculated based on the scattering matrix. Finally the radiation patterns of the array are calculated according to the principle of pattern multiplication.
