Research And Design Of Mobile Terminal Antenna

With the rapid development of the wireless communication system,4G mobile communication technology becomes more and more mature,and is evolving forward to the fifth generation(5G)communication standard gradually.Since the mobile terminals work with multiple modes currently,the antenna in mobile terminals is required to cover multiple frequency bands or a wide frequency band.In order to achieve high data transmission rate,multi-antenna technology is applied widely in modern mobile terminals.However,due to the trend of ultra-thin and multifunctional mobile terminals,the space for antenna system becomes more limited.Based on the above background,this paper focuses on the design of mobile terminal antenna.Firstly,the paper introduces the basic theory of the mobile terminal antennas.Secondly,the paper summarizes the common structures and design methods of mobile terminal antennas.Then the paper proposes three antennas for mobile terminals.The first one is a compact hexa-band planar mobile terminal antenna.The antenna consists of one monopole and two parasitic shorted strips.The miniaturization is achieved by bending radiation and parasitic branches,the multi-band and wideband performances are achieved by adopting the parasitic branches which are coupled-fed.The antenna can cover GSM900,GSM1800/1900,UMTS,and LTE2300/2500 bands fully,and can achieve omnidirectional radiation performance.The overall size of the antenna is 37.5 mm×11.4 mm.The second one is a compact octa-band mobile terminal antenna.The antenna is comprised of one radiation strip,two parasitic strips and an impedance matching circuit.The multi-band and wideband performances are achieved by loading the parasitic shorted strips and the impedance matching circuit.The impedance matching of the antenna is improved by etching several slots on the ground.The antenna is simulated,fabricated and measured;the measured results show that the antenna can cover LTE700,GSM850/900,DCS1800/ PCS1900,UMTS and LTE2300/2500 fully.The measured efficiency of the antenna is 70-87% in low-frequency band and 62-87% in high-frequency band.The third one is a ten-element MIMO antenna for 5G mobile terminals.The antenna consists of six monopoles and four slots with coupled feed.Through optimizing the structure of antennas,the antenna can acquire good impedance matching.Through placing the elements with different radiating modes alternately along the sides of the mobile terminal,the antenna can acquire good isolation.The antenna is simulated,fabricated and measured,the ten elements can cover 3.3-3.6 GHz bands when the return loss is greater than 10 d B;the efficiency of the antenna is about 50-76%;the isolations are better than 11 d B and the envelop correlation coefficient(ECC)is lower than 0.15 between any two antenna elements;and the channel capacity is reached about 48-51 bps/Hz.Moreover,the antenna is printed on a planar substrate,resulting in easy fabrication than solid structure.