Broadband Omnidirectional Stacked Biconical Antenna with Gain Enhancement Based on a Gradient Structure

In this paper, an omnidirectional stacked biconical antenna that can be implemented to achieve broadband and high gain with a gradient biconical structure is proposed. The proposed antenna is constructed by three different biconical elements, in which two of them are composed of a pair of symmetrical cones each loaded with a cylinder and a ring. With this setup, a gain enhancement is achieved in the azimuth plane that corresponds to the omnidirectional radiation, while a broad impedance bandwidth still can be maintained. In the designed prototype, the proposed antenna demonstrates| S 11 | below −10 dB and an omnidirectional radiation pattern over a frequency band from 0.38 GHz to 10.35 GHz. Moreover, simulated results indicate that, the realized gain of antenna in its azimuth plane ranges from 0.45 dBi at 1 GHz to 6.96 dBi at 6 GHz, which is improved by about 0.95 dBi to 5.5 dBi, when compared with conventional designs.