| Wireless body area network is one of the significant technical means for personal health information collection and transmission.The antenna of wearable electronic equipment in WBAN plays a definitive role in the quality of signal transmission.Therefore,the research of stable and secure antenna is of great significance to the realization of body area network communication.In this thesis,a number of flexible antennas working in the ISM open band are designed and their performance is optimized by artificial magnetic conductor(AMC).The primary research contents are as follows:(1)A dual-band textile antenna(2.45GHz/5.8GHz)is designed.Denim material and copper strip are selected as antenna substrate and radiation element respectively.The-10dB bandwidth of low band is 2.29Ghz-2.6GHz,and the-10dB bandwidth of high band is 5.14GHz-6.99GHz.The overall size is 30×20×0.8mm~3,showing advantages in terms of volume and comfort.By analyzing the return loss and radiation efficiency during the deformation process,it is found that with the decrease of the bending radius of the antenna,the greater the influence on the performance of the antenna,the more obvious the radiation efficiency decreases.At the same time,it is found that the proximity of the human body has little impact on the impedance characteristics of the antenna.(2)For the sake of to enhance the reliability of the antenna performance of wearable devices,a dual-band flexible monopole antenna with a 3×3 AMC structure of ISM band is proposed by using meander technology.An annular-shaped AMC is placed directly below the antenna,which can be better suitable for wireless body area network applications.Polyimide substance is used as the antenna substrate,which makes antenna bendable and thin.Benefiting from the in-phase reflective properties of double ring AMC structure,the antenna has good radiation characteristics.Compared with the single antenna,numerical simulation and measure results show that the gain of AMC loaded antenna is increased by 4.54dBi and 3.86dBi at 2.45GHz and 5.8GHz,respectively.Along with,the specific absorption rate(SAR)of 1g is only 0.305W/kg at 2.45GHz and 0.412W/Kg at 5.8GHz when the antenna is placed on human tissue,which is far below the Federal Communications Commission(FCC)standard.The antenna is easy to be conformal with human body and has strong robustness to structural deformation and human body load.(3)In order to adapt to the miniaturization,a dual-band flexible antenna with 2×2 AMC array is designed by multi-branch method.The upper monopole antenna can obtain dualfrequency characteristics by adjusting the relationship between the branches and wavelength,and reduce the antenna size by folding the branches.At the same time,a dual-band structure with miniaturization is obtained by improving the AMC structure under the second antenna.The final overall size of the antenna system is 52×52×5mm~3,covering 2.4GHz-2.485GHz and 5.725GHz-5.85GHz of ISM band.The results indicate that AMC structure can reduce the radiation in force and SAR value of the antenna back lobe,and improve the antenna gain.In addition,the wearable antenna can work normally near human tissues and when bent to a certain degree,which meets the requirements of practical application scenarios. |
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