Design Of Wearable Devices Antenna

With the increasing competition in the smartphone industry,the development of the smartphone industry has encountered a bottleneck.Lots of users hope to use a new kind of mobile terminal product.Wearable mobile terminal products have attracted people's attention.They are light and portable,with various functions,and have great space for development.The most well-known wearable terminal device is smartwatch,that is worn on the wrist of the human.At present,smartwatch has Bluetooth connection,wireless network connection,GPS positioning,calling and other functions.In addition to various functions,most users also put forward requirements for smart watches,such as small size,comfortable wearing,weaker electro-magnetic radiation,faster information transmission speed and so on.Therefore,two watch antennas and two antenna SAR reduction schemes are proposed in this thesis,aiming at the multi-band/broadband coverage,miniaturization,multi-port decoupling,radiation safety and other problems of the antenna of wearable terminal devices.Firstly,this thesis presents a design method that loading parasitic branches on a metal frame antenna,and presents a design idea that the metal frame works at high frequency,and parasitic branches work at low frequency.This thesis designs a single-port multi-band watch antenna,which solves the problems of watch antenna miniaturization and multiband/broadband coverage.The-6d B impedance bandwidth of the final antenna can cover Bluetooth(2.40-2.485GHz),WLAN(2.40-2.483 GHz,5.15-5.825GHz),Wi-Fi 6E(5.925-7.125GHz)and 5G(3.4-3.6GHz,4.8-4.9GHz)bands at the same time.The height of the antenna is 5mm(0.04?),and the size of the antenna is 38.6mm×35.6mm(about 0.31?×0.28?).Secondly,this thesis presents a design idea of hybrid antennas.Based on the characteristic mode theory,this thesis also presents the antenna characteristic current analysis method.It designs a multi-port multi-band watch antenna,which solves the problem of watch antenna multi-port decoupling.The antenna consists of four antenna units,two of which make up the MIMO system and others work at the other operating bands.Finally,the-6d B impedance bandwidth of the MIMO system can cover the dual-band of 2.40-2.485 GHz and 3.4-3.6GHz,and the isolation between units is more than 15 d B in the band,and the envelopment correlation coefficient is less than 0.2.In addition,the-6d B impedance bandwidth of the other two antenna units respectively covers the GPS frequency band(1575MHz±5MHz)and WLAN-5 broadband band(5.15-5.825GHz).The height of the antenna is 5mm(about0.026?),and the size of the antenna is 42mm×42mm(about 0.22?×0.22?).Finally,aiming at the radiation safety problem of the watch antenna,this thesis firstly constructs a simplified human wrist phantom with a cube shape,and designs an original antenna that can work in 2.40-2.483 GHz and 5.725-5.825 GHz.Based on the mechanism of human body electromagnetic energy absorption,two kinds of watch antenna SAR reduction schemes are proposed.The SAR can be simultaneously reduced at 2.45 GHz and 5.8GHz by loading the EBG structure,and the reduction rate is over 70%.Adjusting floor structure method does not need to add additional structures in the space outside the antenna,and the SAR can be reduced at 2.45 GHz,the reduction rate is more than 30%.Therefore,the two watch antennas and the two SAR reduction schemes proposed in this thesis have good application value in the field of wearable terminal devices.