| With the increasing demand for stable and comfortable medical security services,implantable devices have been widely used in wireless capsule endoscopes,pacemakers,blood glucose monitoring systems,etc.,and the performance in wireless medical industry has higher requirements.As an important component in implanted medical devices,implantable antenna provides a channel for wireless information transmission between internal and external devices.Its performance directly affects the quality of date transmission and the results of medical diagnosis,so the design of implantable antennas with good performance is of great significance to the development and application of wireless medicine.In this thesis,according to the technical requirements of implantable antennas in various application scenarios,three implantable antennas for wireless medical are studied and designed.The main work is as follows:1.A miniaturized,high gain implantable antenna resonating at 2.45GHz is designed.The semicircle structure is used as the main radiator of the antenna.The half-ground structure and step feeder are adopted to adjust the resonant point and reduce the overall size.The antenna operates in 2.01～3.10GHz,which is wideband.In order to improve the gain,a zero-refractive covering plate,which is used to regulate the propagation direction of EM waves and focus the energy,is placed on the upper surface of the monopole antenna.The gain of the antenna after loading the covering plate is improved by more than 3.2dB.The overall size of the antenna system is only7×10×0.254mm~3,and the peak gain is-10.2dBi.The antenna achieves high gain performance while miniaturizing the size.2.A miniaturized circularly polarized implantable antenna which operates in2.02～2.74GHz and 3.73～5.59GHz is designed.The antenna that satisfies the symmetry of structure and electric field distribution is cut in half to obtain a compact structure and a wider band.The antenna size is 10.4×10×0.254mm~3.The two operating bands are obtained by loading patch on the radiating surface.The circular polarization performance of the antenna is achieved by exciting orthogonal linearly polarized components on the radiation surface.The important feature is that the antenna has two operating bands,which can realize the dual-mode operation of the implantable devices.And each operating band has circular polarization characteristic3.An ultra-wideband capsule endoscope antenna is designed.The antenna uses a flexible material as a substrate to achieve conformal and to leave room for other devices in Wireless Capsule Endoscope to improve the space utilization.Based on the broadband characteristics of traditional helical antenna,the helical structure of the antenna is improved.In order to improve the impedance matching of the antenna,the short-pin is loaded at the suitable position of the cylindrical feed network.A Complementary Split-Ring Resonator(CSRR)slot is added to the ground of the feed network to realize dual-frequency by utilizing circuit characteristics.The antenna can not only operate in two bands,but also has ultra-wideband.The operating bandwidth in the two bands is 30.3%and 53.3%respectively.All the antennas in this thesis have been fabricated and measured.The pork tissue and human muscle tissue mimicking liquid are selected to replace the antenna working environment.The measurement results are basically consistent with the simulation results,and meet the design indicators of implantable antennas. |
