| With the popularity of the third and fourth generation mobile communication network,the mobile devices have developed rapidly and widely used.The antenna is an important front-end component of the terminal equipment to transmit and receive wireless signal.The terminal antenna has made a big change.With the increase of mobile phone function,the popularity of the metal-frame mobile phone and the application of MIMO antenna technology.In order to design multi-antenna system with high isolation in the metal frame terminal device,the antenna unit should not only meet the miniaturization,broadband,multi-band technical requirements,but also need to overcome the deterioration of the antenna radiation performance by the metal shell.All these changes mentioned above have brought great challenges to the metal-frame terminal MIMO antennas design.In this paper,three common-metal-frame MIMO antennas will be presented.Firstly,this paper analyzed the development of the terminal antenna and the current research situation in the world,then the challenges of the terminal antenna design and the innovation of my job was summarized.The antenna’s basic theory,common types of terminal antenna,the primary technologies of miniaturization,wideband and multiband,the requirement of antenna performance,and the decoupling techniques are presented.Secondly,Common-metal-rim dual antennas capable of providing WIFI band for smartphone applications are presented.Two inverted F antennas share a common metal rim.By inserting a center shorting branch,a common-metal-rim dual-WIFI antennas with higher isolation and good diversity performance are designed.The working mechanism of the proposed antennas is analyzed based on the S-parameters and the surface current distributions.The radiation patterns are measured and the diversity performances are evaluated.At last,by designing a matching networking at the port 1,the antenna unit 1 working bandwidth is increased to cover WIFI and GPS band at the same time.Thirdly,this paper presents a common-metal-frame seven-band reconfigurable LTE MIMO antennas for smart mobile phone applications.The antenna is coupling fed with a U-shaped microstrip line,and the loop mode of the metal loop between the metal rim and ground plane is excited.By using the characteristics of multi-mode resonance of loop antenna and switch reconfiguration technology.The antenna can work at four states to cover seven band by adjusting the on/off states of the switches.According to the loop antenna current distribution,the antenna unit is placed in a reasonable position to get a high isolation between MIMO antennas.The working principle of the proposed antenna is analyzed by current distribution and some important parameters.At last,the MIMO antennas model is fabricated and tested,and the radiation and diversity performance is evaluated.Finally,a multi-antenna system for complete metal frame terminal is proposed which include a seven band LTE antenna and two dual-band WIFI antennas.The three antennas share a common unbroken metal-rim.LTE antenna unit uses a matching network to improve the feeding port impedance matching,and it can cover seven-band.The passive reconfigurable technology is used in WIFI antenna design,and the working band can cover 2.4GHz and 5.8GHz.The working mechanism of the proposed antennas is analyzed in detail by comparing the simulated results and the measured results.The overall antenna efficiency,working band,isolation,and MIMO antenna diversity characteristics are acceptable for practical applications. |
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