Steerable back-to-back Yagi-Uda dipole array

This paper investigates, by means of an exhaustive two-step optimization procedure, the radiation performance limits in elevation of a steerable back-to-back Yagi-Uda dipole array with a common reflector element above a perfect electrically conducting ground plane. A hybrid optimization algorithm comprising of a global search algorithm, namely the Population-Based Incremental Learning algorithm, and a downhill method is used to determine the array dimensions. For each iteration of this optimizer the optimum feeder´s voltage excitation is determined by a grid search. Topologies with different numbers of director elements and several excitation possibilities are investigated. The antenna with a single director element has a beam scanning range to 70° with 1.2 dB gain variation and a gain value above 9.2 dBi. With no director the array can scan up to 60° with a gain variation below 0.9 dB and a gain above 9.4 dBi. Using two directors the beam can be scanned to 80° with a gain above 8.5 dBi and a gain variation of 3.7 dB.