Study On Electromagnetic Radiation Of Wireless Endoscope Capsule Basing On FDTD

Wireless Capsule Endoscope technology is painless and non-invasive,which can detect of digestive tract diseases such as small intestinal erosion,gastric ulcer and so on.But there are still many problems of WCE unsolved,such as the safety of electromagnetic radiation.The antenna is the main radiative component in the capsule endoscopy system which causes the bio-electromagnetic effects to human body.The aim of this paper is to study the electromagnetic radiation safety when antenna is designed for miniaturization.Therefore this article has carried out the following work:First of all,this paper sets up the antenna model with theoretical formulate,and the FDTD method of space electromagnetic field is summarized.At the same time,3D digital real human body model is drawn by the software Varipose,and electromagnetic characteristic parameters of different tissues have been set under the specific frequency in the simulation software XFDTD.Since above work have been finished,the simulation environment has been completed.Besides,this paper lists the standards of electromagnetic radiation safety at home and abroad.Finally chooses ICNIRP,which is the most relevant to medical equipment,as the reference limitation of this study.Next the parameters of antenna are simulated to study the performance of antenna,including the line length,initial polar radius,line radius,screw-pitch?XY plane and Z direction?,the direction of the helix,the dielectric parameters of substrate?dielectric constant,substrate thickness,the distance from substrate to antenna,substrate radius?.Finally,a kind of transmitting antenna is established at the frequency of 2.4GHz,to ensure the following study of electromagnetic radiation safety.Finally,the distribution of electromagnetic radiation in digestive tract is studied,and the electromagnetic radiation safety of human digestive tract is analyzed comparing with the limitation standard.In this paper,the digestive tract is divided with esophagus,stomach,small intestine and large intestine.Total 107 points are evenly selected at each site to simulate the movement of capsule.Then the radiation distribution simulation is guided and discussed at these points.The main parameters SAR RAW,SAR_avg,SAR_10g0g and polar direction are analyzed.Through all points SAR RAW values of digestive track are collected,the distribution characters of the SAR is summarized.The polarization characteristics of antenna in human body are discussed,by observing the polarization direction from the maximum value of SAR_10g at each part of digestive tract.The condition of electromagnetic radiation safety is discussed,by comparing the SAR_10g and SAR_avg with the reference limitation.After changing the input power of antenna,it finds that when the input power under 75mW,the maximum value of SAR_10g is just under2W/kg in the whole digestive tract?locating small intestine?.Meanwhile,the maximum value of SAR_avg is 0.27mW/kg,which is also under the limitation of 80mW/kg.From the observation of SAR distribution in each part of digestive tract concluding,the radiation direction is along the maximum SAR value point.It meets the requirements of the electromagnetic radiation safety design.