Comparison of Four High Performance Dual Polar Antennas for Base Stations

In this paper four types of cross-dipoles antennas, highly compatible to be utilized in base stations of cellular systems, were thoroughly compared: (1) dipoles with sloping-cut arms, (2) dipoles with folded arms, (3) dipoles with helical shape, and (4) dipoles with helical shape and inverted branches. To carry out the comparison, a design of each type of antenna was performed with an objective bandwidth of 1710–1880 MHz and a return loss higher than 15 dB. By computer simulations, some important parameters were examined: mutual coupling, return losses, input impedance, gain stability, beamwidth invariability, cross-pol discrimination and tracking error. From the comparison, it was found that the crossed dipoles with folded arms occupy the lowest volume and have the higher beamwidth stability. On the other hand, the dipoles with helical shape have the lowest mutual coupling, meanwhile the helical dipoles with inverted branches have the higher cross polarization discrimination. To experimentally validate some of these results, a prototype of the crossed dipoles with helical shape was constructed and measured to demonstrate that the simulations are consistent with the real implementation. After all this study is clear that each antenna has advantages and limitations, and depends on the more stringent requirement that a certain application demands, to select one or another type of antenna.