| With the development of the era of electronic science,medical electronic products came into being.Implantation technology can be used to monitor human body information,the real-time information of biomedical telemetry obtained is transmitted to an external antenna through a wireless link,and a biotelemetry system is established.However,the service life of implantable medical devices is also a major problem in the development of medical technology.So the wireless power transfer(WPT)system has provided new possibilities for these implantable medical devices.In this thesis,an ultra-wideband implantable antenna is designed for cardiac pacemakers.Based on the mechanism of magnetic resonance-coupled wireless power transmission,a WPT system for human implantable devices is designed,and then a metamaterial with magnetic negative characteristics is used.Metamaterial has been optimized for the initial WPT system to achieve a highly efficient human implantable WPT system.Finally,a rectifier circuit was designed for the implantable WPT system.The work of this thesis is divided into four parts:1.The investigation and theoretical analysis of the implantable antenna,WPT technology,metamaterial and rectifier circuit laid the foundation for the design of the implantable antenna and the establishment of the WPT system.2.Firstly,based on the PIFA antenna,the 2.4 GHz single-frequency implantable antenna and the miniaturized dual-frequency implantable antenna are designed with the advantages of small size and high gain of the PIFA antenna.The optimization process of the antenna is introduced.The electric field distribution characteristics at the working frequency and the gain of the antenna are discussed.Secondly,in order to apply the power transfer technology based on magnetic resonance to the implantable system,an ultra-wideband implantable antenna with better performance is proposed for the cardiac pacemaker by using the coil antenna form.The antenna is designed to achieve its ultra-wideband characteristics by introducing separate resonant rings.In order to determine its working mechanism,the antenna was analyzed in three modes,and the principle and process of its working frequency excitation were obtained.At the same time,in order to verify whether it is suitable for other implantable devices,the antenna is simulated in different simulation environments,which verifies its wide applicability.In order to ensure biosafety,the bio-material required for the antenna and the SAR value during operation were considered and analyzed.3.An external transmit antenna operating at 430 MHz was first designed,which combined with an ultra-wideband implantable antenna to form an initial WPT system for cardiac pacemakers.Not only the proper transmission distance and transmission efficiency of the system are analyzed,but also the stability of the system is analyzed by the two positional offsets of the implantable antenna.Finally,it is pointed out that the initial system has the disadvantages of close energy transmission distance and low transmission efficiency due to the special environment of human tissue.4.Firstly,the electrical properties of left-handed materials and magnetic negative materials were analyzed,and a magnetic negative metamaterial unit was designed.Then,for the shortcomings of the initial WPT system,a 2×2 metasurface array composed of designed magnetic negative elements is added to the implantable WPT system.Compared with the original system,when the distance between the transmitting and receiving antennas is 50 mm,the transmission coefficient of improved WPT system is 11 d B larger than the original system.Experimental verification proves the reliability of the results.Finally,a rectifier circuit designed for an implantable WPT system and operating at 430 MHz for low input power was designed.At low input power,the efficiency of the rectifier circuit is 70%. |
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