Research On Implantable Circularly Polarized Antennas For Biomedical Applications

With the aging of the population and the improvement of people's health awareness,wireless biomedicine has received more and more attention.Implantable medical devices play an important role in biomedicine and they can accurately measure human physiological information in real time,which provides doctors with diagnostic treatment information and reduces patient's discomfort at the same time.As key components of implantable medical devices,implantable antennas are applied for wireless communication with external devices.Circular polarization technology can be used for implanted antennas to solve problems of polarization mismatch and multipath interference.Therefore,the research on implantable circularly polarized antennas for biomedical applications is significant and valuable.This dissertation was supported in part by the National Natural Science Foundation of China(61372008),in part by the Science and Technology Planning Project of Guangdong Province(2014A010103014,2015B010101006),and studied circularly polarized implantable antennas for biomedical applications.The content mainly includes:(1)A circularly polarized(CP)implantable antenna with complementary spiral resonator: Because of the unique advantage of circularly polarized antenna for communication between implantable devices and external equipment,a circularly polarized implantable antenna is proposed.Through simulation and optimization,the final compact dimension of 10.5 mm × 10.5 mm × 1.27 mm is obtained.The impedance bandwidth is 2.31–2.59 GHz(11.4%)and the axial-ratio bandwidth is 2.41–2.48 GHz(2.86%).The operating principle of the antenna is analyzed,and the effect of the critical parameters on the proposed antenna is studied.By calculating the link margin,the communication link of the antenna is investigated.At last,the antenna is fabricated and measured.The measured results were consistent with the simulation results,verifying the accuracy of the theoretical design.(2)A miniaturized circularly polarized implantable antenna with slow-wave structure: To achieve miniaturization and circular polarization of implantable antenna,a miniaturized circularly polarized implantable antenna covering the 2.45-GHz ISM band is designed.By loading slow wave structure and V-shaped slot on the patch,a compact size of 9.2 mm × 9.2 mm × 1.27 mm is achieved.By introducing perturbation element in the patch,the circular polarization purity of the antenna is optimized.The proposed antenna is placed in the CST human voxel model to verify the performance,and the SAR value of the antenna was evaluated for safety concerns.(3)A circularly polarized antenna for capsule endoscope application: In order to solve the problem of polarization mismatch between the capsule endoscope antenna and the external linear polarized antenna,a circular polarization antenna is proposed for the capsule endoscope.The effect of the substrate,the capsule shell,and the electronic components on the performance of the antenna are analyzed.Finally,the impedance characteristics,axial ratio characteristics,gain and SAR values of the capsule antenna the in different digestive tract organs are discussed.The circularly polarized implantable antennas presented in this article have the characteristics of miniaturization,biocompatibility,and strong anti-interference ability,which can be applied to biomedical implantable devices.The designing methodology of the proposed antennas in this article would provide reference for researches on implantable antennas.