Colinear antennas which have omnidirectional radiation patterns in the horizontal plane are used for base station antenna in personal communication systems because of their easy installation and low cost. For street microcells, which are formed using low base station antenna heights in urban areas, however, colinear antennas yield rather small microcell zones. Zone size can be efficiently increased by using bidirectional antennas which preferentially radiate the antenna beam along the street. The configuration of a bidirectional antenna is automatically determined by the shape of the antenna beam. Accordingly, the optimum beam shape must be determined for realizing the optimum antenna for street microcells. This paper describes the optimum beam shape for street widths ranging from 30 to 60 m, and proposes a base station antenna that yields the desired beam shape. We examine the relation between antenna beamwidth and microcellular zone size. The discussion is based on the theoretical results given by the multi-ray model technique assuming a street microcell model with infinite concrete walls. A bidirectional narrow patch antenna (BNPA) element is developed to realize a bidirectional rod array antenna (BIRA). The validity of the design method used and the antenna's performance are verified by laboratory measurement of a fabricated BIRA operating in the 1.9 GHz band, and field test results.
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