Research Of Sub-6GHz And Mm-wave Antennas In Mobile Handset

With the popularity of all metal frame mobile handset,hand model is one of the key factors affecting the performance of mobile phone antenna,mainly through absorption and reflection to reduce the efficiency of the antenna,change the far field of radiation.Till now,few literatures provide theoretical analysis on the hand effect or systematical method to reduce the effect.In this work,the relationships between the hand effects and the radiation direction of the antennas are investigated using characteristic mode theory.Firstly,we present a typical monopole-loaded mobile phone antenna with metal frames,and calculate its radiation patterns in free space and with hands.Then,we calculate the model of the structure of the antenna.We map the antenna patterns in free space and with hands to the characteristic mode patterns through calculating the weight coefficient of every mode,which stand for the power contributions of the modes.By comparing with the weight coefficient in free space and with hands,it is found that the modes with more radiation along the long side metal border mobile and less radiation in the vertical direction of substrate radiation pattern are more robust to the hands.Finally,according to this conclusion,based on the original antenna structure,a mobile phone antenna with little radiating power towards the boresight is designed.Compared with the reference antenna with the same feeding location,the efficiencies of the proposed antenna with left and the right hand increase by 4.1 dB and 6.3 dB respectively.At the same time,the proposed antenna is tested in free space and with hand,and the measured results are agree reasonably with the simulation ones.In addition,this study also designed a multi-antenna system applied to mobile phones based on leaky wave antennas.Twelve millimeter wave leaky wave antennas were placed on the metal rims of mobile handsets.Different from traditional millimeter wave mobile phone antennas,this antenna system does not need phased array or complex feed network.Two different leaky wave antennas are operated on the-1th spatial harmonic,one is a rectangular leaky wave antenna,the other is a stepped leaky wave antenna,their main lobe point in different directions on the same frequency band,two leaky wave antennas placed on the same substrate integrated waveguide,can form a leaky wave antenna pair to reduce the size of antenna while does not affect the antenna's performance.The antenna system has a coverage bandwidth of26.8-28.3 GHz,and its gain reaches 5.4 dBi for the coverage efficiency of 50%.Compared with the phased array antennas in the literature,the performances of the antenna system are improved.Due to the distributed arrangement,the antenna system is robust to the hand and other components integrated in the mobile handset.The antenna system can be co-designed with the antenna operating at Sub-6GHz frequency band without any additional structure,and the short frame of the mobile handset is used as the radiator of the low-frequency antenna.The whole antenna system has been fabricated on the case of the handset,with the measured results agreeing well with the simulated ones.