| With the increasing of aging population and the number of sub-health groups,mobile medical(mHealth)technology has been paid more and more attention due to its important application in personal health care,and it will lead the trend of future biomedicine development.With implantable medical equipment in human body,the physiological parameters of patient's can be real-time monitored to provide information for disease prevention,diagnosis and treatment.At the same time,it provides patients with a more comfortable treatment environment and services.The data transmits between implantable medical device and the external device through implantable antenna.Miniaturization of the antenna can not only improve the patient's comfort,but also increase it's sensitivity to the implant position in human body,while excellent antenna performance is an important prerequisite for accurate data telemetry.Wireless energy transferring from out side the body can extend life time of implantable medical devices,which is essential for the long-term and stable work.Therefore,as people's living standards and personal health awareness continues to improve,the research on implantable antenna in mHealth and wireless energy transmission is of great value and significance.However,the complex human environment brings new demands and challenges to the designe of implantable antenna design.The implantable antenna and wireless energy transmission technology used in mHealth is studied in this paper.The main work includes:By employing substrate with high dielectric constant and meandering structure PI FA structure,a compact implantable antenna for biomedical application is proposed,the size of the antenna is 20mm×15mm × 0.5mm,with an operating frequency in medical implant communication services band(MICS band:402-405 MHz),wireless medical telemetry services band(WMTS band:1395-1400MHz)and industrial scientific medical band(ISM band:2.4-2.48GHz).After optimizing,the impedance bandwidth of the antenna at three frequencies is 382-416MHz(8.4%),1.41-1.48GHz(4.9%)and 2.28-2.6GHz(13.1%),and the far field gain is-37.3,-25.7 and-19.1dB respectively.For the designed implantable antenna,the influence on radiation performance of the antenna of different implant position is analyzed.In order to reduce the antenna size,by employing substrate with high dielectric constant and stacked PIFA structure,a triple band antenna is designed,the antenna also covers the MICS band and WMTS band,it also covers the ISM band(918MHz).The antenna structure is compact and have a size of 10mm × 10mm × 1.5mm.Finally,the return loss of the antenna at each frequency is less than-15dB,the gain is-39,-32.-26dB,which ensures the working reliability of the antenna.At the same time,the specific absorption rate(SAR)distribution is evaluated for safety concerns.Finally,the antenna is tested in miced pork and.the measured data is in good agreement with the simulation results.In order to solve the problem of power supply in medical implanted devices,the technology of wireless energy transmission is systematically studied.Based on the designed implantable antenna,safety conditions are considered to establish the transmitter power,thus to establish the received power level of the implantable antenna.To improve the conversion efficiency,the rectifier circuit load,capacitance and inductance are optimized.Eventually,a 69.4%conversion efficiency and a DC voltage of 3.5V is achieved with an input power of 5 dBm,which is sufficient for implantable medical devices. |
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