| With the maturity of third-generation mobile communication systems and rapid developing of the long term evolution network, smartphones are more widely applied in the modern communication system. In the current wireless communication systems, the mobile phones should be applicable for the LTE band application and at the same time they should be compatible for the second and third generation communication systems, thus the mobile phone antennas are essentially to be capable of multiband and wideband operation. In addition, MIMO techniques have been adopted by LTE communication systems, it means there is less area available for the antenna elements. Besides, due to the size limitation of the smartphones, there are strong couplings between the antenna elements. Strong couplings will decrease the antenna efficiency and reduce the radiation diversity which influences the effectiveness of the whole mobile phone system. At the same time due to the work mechanism of the mobile phone and the habit of the users, the radiation will affect the human body continuously and the body phantom will also have impact on the cellphones. Thus to make research on the mutual influence between the mobile phone and human body have great research value. Accordingly, this paper will focus on the bandwidth enhancement of the MIMO antenna, decoupling strategy between the elements and the mutual effect of the mobile phone antenna and the human body, the contents will include the followings:First of all, the background of the mobile phone is briefly described and the development of small antennas is investigated. A general summary of various antenna types is presented to study the wideband impedance matching techniques and explore the solutions to achieve wide band coverage with small size occupation. Besides, the effect of elements displacement on the antenna is also discussed to make preparation for the MIMO antenna design.Then among the wideband single antenna designs, small sized ones are chosen to make the MIMO antenna designs, explore the difference between the single antenna and the multi-antenna system, make further investigation on the designing parameters and guarantee that the antenna elements have full coverage of the desired bands. The advantage and disadvantage of the decoupling schemes are both discussed to find better decoupling strategy. The decoupling schemes with high isolating performance and good practicability are applied in the MIMO antenna design. The simulation is conducted in the full wave simulation software HFSS and the measurement are done by the network analyzer and SATIMO chamber. The results indicate that the proposed scheme in this article has compact size occupation with stable performance and can be applied to various practical mobile phone antenna designs.Moreover, the mutual effect between the mobile phone antennas and the body under the application situation is investigated. Simulated models are built up according to the users’ habit. The effects of hand and head on the mobile phone MIMO antennas in different applied situation are analyzed. These results of the mutual effect between the antenna and human body can contribute to the future MIMO antenna designs to have more reasonable configuration.Finally, the paper will make a summery on the MIMO antenna designs from the prospects of the bandwidth enhancement, decoupling strategies and feasibility of the whole scheme. Meanwhile, the mutual effect between the MIMO antennas and human body is concluded to provide the design specifics for the mobile phone wideband compact MIMO antenna designs. |
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