Broadband Horizontally Polarized Omnidirectional Antenna Array for Base-Station Applications

This communication presents a broadband horizontally polarized (HP) omnidirectional antenna array with low gain variation for base-station applications. It consists of six omnidirectional antenna units. In order to generate HP omnidirectional radiation patterns for each unit, three wideband planar dipoles are employed as basic elements and they are connected by a wideband three-way power divider with equal magnitude and phase, conducting as a loop antenna. Based on such a configuration, the antenna unit obtains an HP omnidirectional pattern as well as a wide bandwidth of 48.2% (VSWR <; 1.5 within 1.67-2.73 GHz). However, the gain variation is more than 2.5 dB, which is relatively large. To reduce the gain variation, a novel approach is proposed by dividing the six antenna units into three unit pairs. Each unit pair consists of two antenna units which are complementary in radiation pattern. Using this method, the number of basic elements in each antenna unit is not increased, but the simulated gain variation is effectively reduced to about 1.24 dB.