Wearable Antenna Design Based On EBG Structure

With the launch of 5G commercial use in 2020 and the advent of the Internet of everything era,wearable experience device is becoming an important carrier of terminal applications.As an important part of human-object communication,wearable antenna has been widely studied and applied in medical,military,communication and other fields.At present,the wearable antenna is gradually developing towards miniaturization,wide band and high gain.At the same time,the electromagnetic wave radiated by the antenna will have a heating effect on human biological tissues,it is also an important research content of the wearable antenna to improve the isolation between the human body and the wearable antenna.In this paper,based on the basic theory of microstrip antenna and Electromagnetic Band Gap(EBG),four kinds of wearbale antenna systems are designed to meet the requirements of applications.The specific work of this paper are as follows:1.Two wearable antenna systems loaded with new EBG structure are designed.The in-phase reflection characteristics of EBG structure and the surface wave bandgap characteristics are respectively verified in improving the radiating indexes of the wearable antenna.The first structure uses a monopole antenna as a radiator,when the EBG reflecter with in-phase reflection character is loaded at the bottom of the antenna,the gain and the front to backward ratio of antenna can be increased by 4.55 d Bi and 22 d B respectivly.The elect field distribution of antenna system with three-layer human tissue model is observed.The simulation results show that the Specific Absorption Rate(SAR)is reduced by more than 95% when loading the EBG reflector.The antenna system is fabricated and tested in different parts of the human body.the simulation resules are well consistent with the measured ones.In the second structure,the fractal technology is taken in design of a compact UC-EBG cell,through the method of microstrip line detection and parameter optimization,the range of EBG band gap can be adjustd to cover the antenna operating frequency band.Meanwhile,the electric field distribution of antenna system is observed in combination with the human model.The simulation results show that the use of EBG reflecter can reduce the backward radiation of antenna without losing the bandwidth and reduce the SAR value by more than 90% in the range of human tissue depth less than 12 mm.The structure verifies the feasibility of improving the antenna radiation index with the EGB surface wave bandgap characteristics.2.Aiming at the technology trend of the miniaturization and the application demand of easy conformal,two miniatured wearable antenna systems are designed.The first structure reduced the antenna size by more than 45% by loading lumped inductance into the branches of the antenna.When the antenna is loaded on top of the annular EGB array,the antenna gain can be increased by 3.7d Bi,and the front to back ratio can be increased by 22 d B,and the SAR value conforms to the defined standard.In the second antenna system,the curving flow design of windowed-EBG cell structure extends the equivalent current path and which makes the structure more compact.The windowed-EBG array is placed at the bottom of the antenna and a human model is built to observe the relevant electrical indicators.The antenna system had good robustness under different bending radians and the overall size of system is just 0.48?g.