Design of Wideband Base Station Antenna by Involving Fragment-Type Structures on Dipole Arms

Base station antenna usually requires dual polarization operation with satisfactory input return loss, adequate dual-polarization isolation, stable gain and half-power beamwidth in a wide bandwidth covering the entire or part of the mobile communication bands. Such comprehensive requirements provoke great challenges in antenna design. A novel design scheme is proposed by involving fragment-type structures (FTS) in antenna, and seeking for the optimal FTS by multi-objective optimization searching. The technique is demonstrated by improving crossed dipoles for operation in band ranging from 1.7 GHz to 3.8 GHz. Part of the dipole arms can be gridded into cells and re-configured by using FTS elements. For automatic optimization searching, binary coding scheme for both the FTS distributions and canonical dipole structure dimensions is proposed. Simulation and measurement show that the optimal crossed dipole antenna may acquire a wide operation bandwidth of 76.3%, with the return loss higher than 15 dB, isolation higher than 30 dB, half-power beamwidth of 65° ± 5°, and gain of 9 ± 0.65 dBi for ±45° polarizations.