| As the number of wearable electronic devices increases,multiple devices operating simultaneously in dense environment will make high-speed wireless transmission difficult to realize,or even the connection is interrupted or no service,what's worse,it would affects some wearable devices if they require high speed trasimission.Millimeter-wave antennas could relieve these problems to some extend and have been widely concerned for their high speed,wide bandwidth and anti-interference in some sperturms.This work was supported in part by the National Natural Science Foundation of China(61372008),and in part by the Science and Technology Planning Projects of Guangdong Province(2014A010103014,2015B010101006).Based on the requirements of the wearable networks,research would mainly include millimeter-wave directional off-body antenna,millimeter-wave omnidirectional on-body antenna and millimeter-wave on-/off-body large frequency ratio antenna.More details are as follows:(1)A high gain millimeter-wave wearable directional antenna operating in ISM band(61-61.5 GHz)is proposed.The antenna applies the principle of Yagi-Uda antenna with five layers of disks as the directors.The measured bandwidth is also broadened to 15.1%(57.58-67GHz)and the simulated bandwidth of gain with more than 10 d Bi is 17.9%(57.99-68.97 GHz)with a radiation efficiency over 85%by the addition of these layers.The proposed antenna is a candidate for off-body devices with peak specific absorption of 0.7855 W/kg and peak power density of 7.757 W/m~2.To connect devices wearing on human body and extracorporeal devices,an omnidirectional millimeter-wave on-body antenna is presented.(2)A millimeter-wave wearable omnidirectional antenna operating in ISM band(61-61.5 GHz)is proposed.The principle of Yagi antenna is also applied to the antenna.The structure of the main driven element is similar to the monopole.To reduce the the interaction between the whole antenna and human body,the easiest way is to utilize a full ground.A branch is added behind the monopole as a reflector to enhance the directivity and horizontal peak gain of the antenna.The designed antenna with the measured bandwidth 57-67 GHz(16.1%)realizes a good omnidirectional whose gain variation in the horizontal direction is less than 1.8d B,and the maximum gain at 61.25 GHz is 7.04 d Bi.The antenna with the radiation efficiency over 90%could conform to the limits of FCC and ICNIRP for the specific absorption is less than 1.386 W/kg and the power density is less than 8.562 W/m~2.What's more,the interconnection between implantable devices and wearable devices can greatly improve the efficiency of interconnection among body area networks.Therefore,it is necessary to design a wearable antenna to combine the advantages of microwave and millimeter-wave antennas.(3)A flexible wearable antenna with large frequency ratio for on-/off-mode is investigated,which is applied to receive and transmit signals from both microwave band(2.4-2.5 GHz)and millimeter-wave band(24-24.5 GHz)of ISM band.The antenna covers 22.34-25.52 GHz(13.3%)with the gain over 5 d Bi and 2-2.52 GHz(23%)with the gain over 0.1093d Bi which could communicate with implanted antennas within 5 meters.When the input power is 0.38 W,the maximum SAR of the antenna is 0.9546 W/kg at microwave part,0.7935 W/kg at millimeter-wave part and the power density of millimeter-wave part is 7.761 W/m~2,which meets the limits of ICNIRP and FCC.The antenna with the merits of dual-band dual mode,good directivity in millimeter-wave band,and good omnidirectional in microwave band could still cover ISM band when it endures bending.According to the research above,millimeter-wave antennas in wearable system networks are enriched,which paves the way for the practical engineering application of interconnection of wearable systems. |
PDF Full Text Request