Research On Flexible Wearable Broadband Antenna

In recent years,the development of the fifth-generation mobile communication technology has accelerated the relevant research in the field of wireless body area networks(WBAN)centered on the human body.As an important part of the human body wireless body area network,wearable antennas have broad application prospects in military,biomedical and entertainment life.However,wearable antennas based on traditional technology and materials can no longer meet the increasing requirements of modern communication systems for broadband,light weight,flexibility,low profile,and easy integration of the human body.Combining new flexible materials,this paper mainly studies the broadband design of wearable antennas based on new flexible materials from the perspective of engineering applications.At the same time,combined with the human body voxel model to study the interaction between the wearable antenna and the human body,the specific absorption rate(SAR)analysis and suppression technologies.The main research work can be summarized as follows:1.According to the theory of planar broadband printed antennas,the structure design of graphene-based flexible ultra-wideband wearable antennas is completed by means of gradual structure,slotting and other broadband methods.The antenna is made of high-conductivity graphene film and polyimide dielectric substrate.The performance changes of the antenna under different bending radii and the performance stability of the antenna when it is loaded on different areas of the human body surface are studied.The simulation and test results show that the antenna has good consistency in free space and under the condition of loaded with human tissues.The impedance bandwidth of S₁₁<-10dB is 0.34-1.4 GHz,and the pattern has the characteristics of horizontal omnidirectional coverage.2.The in-phase reflection characteristics of electromagnetic band gap(EBG)structure is studied and a multi-layer flexible wearable broadband antenna based on the Uniplanar Compact Electromagnetic Band Gap(UC-EBG)structure is proposed.Firstly,based on the square radiation patch,a broadband monopole flexible wearable antenna is designed by slotting and corner cutting.Secondly,a UC-EBG unit structure is designed to suppress the back radiation of the wearable antenna and reduce the SAR of human tissue.Then the UC-EBG is placed under the flexible monopole wearable antenna as a ground plate in a 5×6array,which enables the combined antenna to improve forward radiation gain and suppress backward radiation.It also realizes that the specific absorption rate of human tissue meets the safety standards of international organizations for electromagnetic radiation.Finally,combined with the three-dimensional voxel model of human body,it is verified that the antenna has stable wearable performance.The-10dB bandwidth of the antenna is 4.5-6.82GHz(41%),and the maximum gain achieved after loading human tissue is 8.5dBi.In addition,a high gain,broadband array antenna is designed based on this,which achieves gain of 11.8-13.97dBi in the band ranging from 4.5 GHz to 6.5 GHz.The sidelobe level of the antenna is less than-12dB and the cross polarization is less than-17dB,and it has good electrical performances.