A Multiband Dual-Polarized Omnidirectional Antenna For 2G/3G/LTE Applications

Omnidirectional antenna has the advantages of 360° full coverage and supporting a free alignment between the receiving and transmitting antennas.In order to realize the advantages,many kinds of antenna structure are applied to omnidirectional antenna,such as dipole,patch antenna,planar antenna,but these designs are generally narrow band structures.On the other hand,dual-polarized antenna could improve channel capacity and mitigate polarization mismatch by providing two cross-polarized independent channels.Dual polarized antennas are also keys to improve MIMO throughput in long term evolution(LTE)systems.For now 5G is hot topic,but 2G/3G/LTE antenna will still play an important role in a long term for the universality and practicability of it.According to the above facts,the design of multiband dual-polarized omnidirectional antenna is needed in mobile communication systems.A multiband dual-polarized omnidirectional antenna is proposed in this paper,which consists of horizontal polarization(HP)and vertical polarization(VP)element with separate feeds.The main work and achievements of this paper are:(1)The HP element consists of three wide band,high gain electromagnetic structures(WHEMS),which is nested on the top of the VP elements.The bandwidth of HP element for return loss(RL)>10dB is 55%(1650-2900MHz),covering the multiband 3G/LTE.After folding the WHEMS element,the HP element realizes a good omnidirectional radiation pattern in the LTE band.(2)The VP element consists of three polygonal radiation patches with three equally-spaced legs shorted to the ground plane.The bandwidth of VP element for RL>lOdB is 108%(780-2700MHz),covering the multiband 2G/3G/LTE.The gain of VP element is more than 5dBi in LTE band and 1.5dBi in 2G band.(3)The HP element is nested on the top of the VP elements.Since three WHEMS elements are folded,the VP elements can be used as three corner reflectors for HP element,improving the gain of HP element.The gain of HP element is more than 3 dBi in LTE band after the nesting.The proposed antenna can be applied in mobile communications.