Research On High Isolation MIMO Antenna Technology For Mobile Terminals

As an important device for transmitting and receiving information data,the mobile terminal antenna is one of the essential components of the mobile product.Next-generation communication technologies have imposed higher requirements on the channel capacity,transmission rate,and reliability of mobile communication systems.Under these requirements,multi-antenna technology or Multiple-In Multiple-Out(MIMO)technology has become an integral part of current and future wireless communication systems.However,when these technologies are applied to mobile terminals that tend to be miniaturized,the limited space makes the coupling between the antenna large,and also results in the degradation and deterioration of the antenna performance.Therefore,this thesis focuses on high isolation MIMO antenna technology in mobile terminals.The main work of this thesis is as follows: 1.The multi-feed MIMO antenna technology is studied.By setting multiple feeding ports,the single radiator achieves equivalent multi-antenna performance,and each feed port has high isolation,low correlation and high efficiency.Based on multi-feed antenna technology,a pair of symmetric structure of a dual-feed MIMO antenna is designed.The antenna operates in the frequency band from 3.4 to 3.6 GHz.Then a pair of asymmetrical dual-feed MIMO antenna is proposed.The proposed antenna pair achieves high isolation by properly adjusting the distance between the two feeding ports and the position and length of shorting strips on the radiator.In the desired frequency band,the isolation between the two feeding ports is over 23 dB.Compared with the symmetric dual-feed MIMO antenna,the structure of the proposed antenna is simpler,the form is more flexible.Then,a slotted quadruple-feed MIMO antenna is proposed by using the working mechanism of the asymmetrical dual-feed MIMO antenna.The detailed analysis and explanation are given.Since the slot changes the shape of the ground,it may be difficult to use in an actual mobile terminal.Therefore,we design a quadruple-feed MIMO antenna that does not need to change the shape of the ground.The structure of the antenna is simple,and no additional circuit or structure is required.Port isolation and efficiency is high.The measured results show that the designed dual-feed and quadruple-feed MIMO antennas have good performance.2.Two decoupling designs for the initial dual-band MIMO antenna have been completed.Three dummy elements with open-ended impedance loads are used to implement decoupling design of dual-band antenna.The design flow of the antenna is elaborated,and several important steps are explained in detail.The simulated and measured results show that the isolation of the initial dual-band antenna is increased from 8 dB to 20 dB above the desired frequency band of 2.4 to 2.5 GHz and 5.7 to 5.9 GHz,and the envelope correlation coefficient drops significantly.However,the total efficiency in the high frequency band decreases.In order to simplify the antenna structure and make the radiation performance of the antenna stable,a single dual-band dummy element with an open-ended impendance line is used instead of three single-band dummy elements to achieve dual-band antenna decoupling design.Simulation and test results show the effectiveness of the design method.