A dual-band printed dipole antenna with integrated balun covering UMTS and WiMAX bands

In this paper, a uniplanar dual-band dipole antenna merged with an asymmetrical broadside-coupled balun that offers wideband impedance matching is presented. The balun has compact size and simple layout profile; on the other hand, its shape can be arbitrarily changed as long as the determined centerline length is maintained. By properly increasing the spacing between the long-arm and short-arm dipoles, the effect of the mutual coupling is improved such that dual-band frequency characteristics can be controlled and optimized, respectively. To validate the transition capability of the proposed balun, the balun has been employed to feed the dual-band antenna. Measurements show that the peak gains in the lower and upper bands are 3 dBi@ 2 GHz and 4 dBi@ 3.5 GHz, respectively, and the radiation patterns are almost omnidirectional at H-plane.