| Body area communication has broad application prospects in fields such as smart healthcare,remote healthcare,and sensory networks.Implantable and wearable antennas are important components for achieving body area communication.As important indicators of antenna,miniaturization of antennas can reduce discomfort when implanted inside the human body or worn on the surface of the body.Antennas with wide bandwidth can work more stably in different body types and different parts of the body.Based on this,this dissertation studies and designs the miniaturization and broadband of implantable and wearable antennas,with the main content as follows:(1)Design of implanted and external antennas for Human Body Communication(HBC)frequency band.HBC frequency band has low electromagnetic energy attenuation and weak radiation to the human body,but the antenna size is difficult to miniaturize.This dissertation designs a small HBC antenna using 1 mm thick FR4 material.The radiating part adopts a square spiral structure and ground slot to reduce the antenna size,and the radiating part is connected to the ground through a via hole to improve the antenna bandwidth.The antenna area is 10×20 mm~2,and the-10 d B bandwidth tested in muscle is40-46.4 MHz.This dissertation also designs an external HBC antenna with the size of30×30×1 mm~3,and the placement status of the internal and external antennas are analyzed for their impact on transmission performance.The test results show that when the operating frequency is 43.6 MHz,the transmission coefficient of the system is-16.6 d B and the power transmission efficiency is 1.7%.Compared with existing implanted HBC antennas,the designed antenna in this dissertation has a smaller size and wider bandwidth.(2)Design of implantable antenna and external receiving antenna for the Industrial,Scientific,and Medical(ISM)2.4GHz band.The small antennas in ISM 2.4GHz band have a narrow bandwidth.When implanted in different human tissues with significantly different dielectric properties,the resonant frequency of the antenna varies greatly,making it difficult to cover the entire working frequency band.To address this issue,this paper proposes a small implantable antenna that works well in both fat and muscle tissues.The radiating part of the antenna consists of two square spiral structures that can excite two resonances.The first resonance covers the ISM 2.4GHz band in fat,while the second resonance covers the same band in muscle.The antenna is printed on a 70μm thick polyimide substrate with an area of 2×7 mm~2.The bandwidth tested in fat is 2.23-2.62GHz,and in muscle it is 2.12-2.68 GHz.This paper also designs a small external receiving antenna that is printed on a 1mm thick FR4 substrate with an area of 50×50mm~2,and analyzes the effect of the distance between the transmitting and receiving antennas on the transmission performance.The test results show that at 2.45 GHz,the transmission coefficient of the system is-29.1 d B,and the power transmission efficiency is 0.12%.The proposed implantable antenna has the characteristics of being small and flexible,with a width of only 2mm,suitable for needle insertion.It can cover the working bandwidth in both fat and muscle tissues.The performance of this antenna is better than that of existing ISM 2.4GHz band implantable antennas.(3)Wearable antenna design for ultra-wideband(UWB)frequency band.A UWB array antenna with a flexible polyimide substrate was designed for wearable devices for extracorporeal communication.The antenna unit is fed by coplanar waveguide to obtain ultra-wideband characteristics.The three units are fed in series to form linear array.The reflector plate is loaded below the antenna to realize directional radiation.The antenna size is 55×121×23.07 mm~3,the tested bandwidth is 3.1-11.3 GHz,and the test gain is 7.9d B,7.3 d B and 8.6 d B at 3.5 GHz,5 GHz and 8.5 GHz,respectively.Compared with the existing wearable antennas,the antenna in this dissertation is compact in size,wide in width and high in gain. |
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