Omni-directional dipole-based wideband planar antenna with capacitive end loading for WiMAX applications

In this paper, a low-profile, omni-directional, and wideband planar antenna for WiMAX applications is proposed. While two additional tightly-coupled open stubs were introduced to the dipole-based radiator to achieve broadband operation, capacitive loading at the ends of the main radiator provided further length reduction. A 30% reduction in length can be achieved through capacitive loading compared to the conventional half-wavelength dipole. Moreover, through introduction of the two additional open stubs, the proposed antenna is able to achieve a bandwidth of 58% from 3.4 GHz up to 6.2 GHz (S ₁₁ < -10 dB), which is at least four times the bandwidth of regular dipole antenna. Meanwhile, Omni-directional radiation patterns with maximum gain of 2.0 dBi and overall radiation efficiency of greater than 76% were maintained.