Magnetic Dipole Antenna And Its Application In Implantable And Wearable Systems

With the development of the medicine,mobile healthcare will be an important step in the field of the medicine.Wearable and implantable devices,as the necessary equipment to be used in mobile healthcare,have been paid great attention and ensure an all-round development.But the technology of the wearable and implantable antenna needs breakthrough,because of the influence from the lossy organisms.Traditional implantable antenna has an excellent performance on a single indicator,but it is hard to obtain large bandwidth and high gain at the same time with a miniaturized antenna in the lossy tissue.In this work,an implantable antenna is proposed which can cover specific medical bandwidth and achieve high gain.On the basis of the implantable antenna,the wearable antenna for the application of the brain imaging and the smartphone has been designed.For the implantable antenna,we analytically derive the electromagnetic(EM)fields of the electric and magnetic dipoles in the lossy human tissue and compare their radiation performance in this work.Based on the analysis,a coupled small loop antenna is designed.The antenna is composed of an inner loop and an outer loop with printed capacitive structures.It can obtain a large bandwidth of 74.1% when embedded in the muscle,showing strong robustness to the change of the implantation environment properties.Compared with other implantable antennas,a relatively high gain of-23.19 d Bi has been achieved and this antenna suffers from less power dissipation in the human tissue ensuring the reliable communication link.The specific absorption rate(SAR)of the antenna is 177 W/kg with an input power of 1W according to the IEEE standard.The planar and cylindrical antenna prototypes were fabricated measured in the minced pork,which has similar EM properties as the human muscle.The simulated and measured results basically agree with each other.The proposed implantable antenna is competitive in its balanced performance of wide band,high gain,low profile,and low SAR.For the wearable antenna,the structure of the implantable antenna is adjusted to design the brain imaging antenna and the smartwatch antenna.The feeding structure of CPW is used for feeding substituting the discrete port.The antenna is attached on the head phantom in the simulation achieving a big bandwidth covering 1.5-4.0 GHz.Compared with the other antennas,the proposed antenna has realized three resonance points and greater impulse purity.The transmitting signal is achieved by using eight-antenna array after simplifying the head phantom.And the result of the brain imaging with the tumor has been drawn by using the algorithm of the local imaging.Then the smartwatch antenna is designed on the basis of the split ring resonator.The antenna is put on the three-layer human wrist phantom for simulation.The proposed antenna can be matched well both in the lower band and the ISM 2.4 GHz band.The total SAR of the antenna is 10 W/kg according to the security standard.The patterns of the antenna ensure that the antenna can receive the signals from all directions.Hence,the magnetic loop antenna can also be applied in the field of the wearable antenna.