Research On Implantable Circularly Polarized Antenna And MIMO Antenna For Wireless Health Care

Wireless implantable medical devices（WIMDs）are used to monitor various pathological data of the human body,enabling medical staff to diagnose and treat patients promptly and effectively,thereby ensuring their health.The implanted antenna is an important component of the device,used for wireless data transmission and reception with external devices.Due to the complexity and heterogeneity of the human tissue environment,it brings some more stringent requirements for antenna design,such as miniaturization,bandwidth enhancement,circular polarization,high gain,human safety,high data rate,and mitigation of detuning effects.Implantable antennas with circular polarization have better mobility and lower bit error rates in medical environments.In addition,to transmit high-resolution image information in real-time and overcome the low data rate of single input single output configuration,MIMO topology is a solution that can improve data rate and communication quality without increasing the input power of antennas.Furthermore,a wide bandwidth can effectively mitigate the detuning of implantable antennas in heterogeneous human tissues.Therefore,to meet the challenges of implantable antenna design,this thesis focuses on researching parasitic element loading technology in the direction of bandwidth enhancement,miniaturization,and circular polarization,with implantable circularly polarized antennas and MIMO antennas as research topics.The main research contents include:1.Compact and broadband circularly polarized implantable antenna design.The antenna operates at 2.45 GHz,with its entire dimension of 9.8 mm×9.8 mm×0.889 mm.For size reduction,a modified square ring with a mitered cross inside is adopted as the main radiator.By splitting one arm of the mitered cross,the compactness can be further improved while exciting the potential CP radiation.The stacked parasitic structure not only ensures 3 d B axial ratio bandwidth of 28.7%,but also helps to achieve-10 d B impedance bandwidth of 30%,with a peak realized gain of-24.7 d Bic.Next,the antenna was integrated into two types of dummy WIMDs and analyzed in the human phantoms（scalp and heart）to evaluate its device-level performance and robustness.Finally,a fabricated prototype was measured in the minced pork,and the measured results agree with the simulated ones.2.Ultrawideband implantable MIMO antenna design.The combination of ultrawideband characteristics and MIMO technology is used in the telemetry field of implantable antennas.The antenna has a compact size of 9×9×0.508 mm³.By loading an H-shaped parasitic element on top of the superstrate to improve impedance matching,the antenna achieves a wide bandwidth of 63.6%,including three important frequency bands,suitable for deep tissue implants.The MIMO antenna consists of two elements with a spacing of 0.6 mm and shares a slotted ground plane,achieving high isolation.The|S₂₁|is below-20 d B in both simulation and testing within the ultrawide operating frequency band.The antenna was integrated with other virtual electronic components to evaluate its robustness by comparing and analyzing the situation before and after integration.Finally,MIMO channel parameters and security performance are also studied.