Research On Wearable Antennas For Wireless Body Area Network Communicatio

With the rapid development of information technology,various communication technologies continue to be updated and iterated.Among them,body-centric wireless body area network has emerged in military,medical,entertainment and other fields.Antenna is a key component in communication systems.While body area network communication brings opportunities to the development of antennas,the increasingly complex communication environment also poses enormous challenges to the design of wearable antennas.On the one hand,the application of wearable antennas in scenes around the human body puts forward higher requirements for miniaturization,broadband,and radiation characteristics of wearable antennas.On the other hand,as a medium with high dielectric constant and high loss,wearable antennas work around the human body,which can easily affect its performance.Moreover,for health reasons,the specific absorption rate（SAR）of antenna radiation to human tissues should be controlled within a safe range.Therefore,it is of great significance to design wearable antennas with different radiation patterns and polarization characteristics based on different application scenarios,as well as to achieve miniaturization and broadband of wearable antennas.The specific content of this study includes:1.Research on dual-band and dual-mode wearable antenna.In this design,a circular microstrip patch with rich modes is selected and fed through a single port,which can work in the industrial,scientific and medical（ISM）frequency bands of 2.45 GHz and 5.8 GHz,respectively.TM₀₁mode is excited at low frequency to generate omnidirectional radiation,which is suitable for on-body communication.In the high frequency band,TM₁₁mode is excited to form a circular polarization broadside radiation pattern to meet the needs of off-body communication.The measurement results are highly consistent with the simulation results.In addition,a human tissue model is established to evaluate the impact of the human body on antenna performance and SAR,respectively.2.Research on broadband circularly polarized flexible wearable antenna.Firstly,in order to improve the wearability of the antenna,the electromagnetic characteristic parameters of a flexible felt material were measured based on the transmission line theory,and the process of manufacturing wearable antennas using flexible materials was explored.For the antenna design,the metasurface antenna with low profile and broadband characteristics was selected.Based on surface wave theory,the broadband principle of uniform metasurface antenna was analyzed,and the metasurface structure was further optimized according to the current distribution,which not only overcomes the problem of gain reduction,but also achieves44.3%of the axial ratio bandwidth.3.Broadband miniaturized flexible wearable antenna to improve the radiation pattern of high-order mode.Aiming at the problem of large size of metasurface antenna and distortion of high-order mode pattern,the miniaturization principle of metasurface is first described,and the operating frequencies of traditional metasurface,cross-layer structure metasurface and short-circuited cross-layer structure metasurface are compared under the same size.Based on this,the antenna structure is targeted and optimized using the characteristic mode analysis theory.By partially loading shorting pins,the antiphase current under high-order mode is suppressed,thereby significantly improving the radiation pattern of high-order mode.In addition,key parameters that affect antenna performance are analyzed,which can effectively guide antenna design.