Design of sleeve broadband antenna for mobile terminals

In recent years, terminal equipment has been developed more multi-band and integrated. In order to reduce the interference between antennas and realize the feature of simpleness, the design of broadband antenna has become the focus of research. Because of the limited spaces of the mobile terminals, the antenna gain, bandwidth and roundness of pattern are the difficult points of designing the sleeve antennas. Combined with the actual application of terminal equipment, a bandwidth of 300 MHz ~ 700 MHz monopole sleeve antenna is proposed in this paper. In this design, the antenna band is broadened by adding the conical sleeve and helical structure on the top of the antenna. The proposed antenna also adopts double sleeve structure to improve the impedance matching. The length of the proposed antenna is 165 mm and the diameter is 9 mm. Good performances of proposed antenna over the operating bands are also obtained. The measured results show that the below -6 dB S
₁₁
(dB) of the proposed antenna can cover the bands from 300 to 700 MHz.