The Electromagnetic Radiation SAR Simulation Calculation And Actual Measurement Of Smart Watches

As a device that improves the weight and wearability of traditional communication devices,smart watches use wireless communication technology that generates a certain amount of electromagnetic radiation,which will induce electromagnetic fields in the body and cause certain damage to organs and tissues.At present,the Specific Absorption Rate（SAR）is considered to be able to more accurately reflect the amount of electromagnetic radiation absorbed by the human body from smart watches.Specific Absorption Rate（SAR）is considered to accurately reflect the amount of electromagnetic radiation absorbed by the human body.In this thesis,finite-difference time-domain Method（FDTD）,a commonly used electromagnetic simulation method,is used to conduct a simulation experiment on SAR of smart watches,and suggestions are put forward for improving the test method of specific absorption rate of smart watches in the current industry standard.The work done in this thesis is as follows:（1）Briefly introduce the damage caused by human exposure to the electromagnetic environment,the research status of the measurement of SAR at home and abroad,and the relevant standards for the SAR value of smart watches.According to the standard "YD/T1644.2-2011",use the DASY6 specific absorption rate measurement system to measure the specific absorption rate of a smart watch;（2）The common method of electromagnetic simulation is introduced: finite difference time domain method,which abstracts and simplifies the test arrangement of the specific absorption rate of smart watches.The flat phantom used in the test was simulated using the simulation space,and the material with the same electromagnetic parameters as the body simulated tissue fluid was added inside the simulation space.The simulation space is divided into units,and the magnitude of the electromagnetic radiation field is calculated by discretizing Maxwell’s equations.Using the finite difference approximation,new values of the electric and magnetic fields are calculated,and the specific absorption rate is calculated using the specific absorption rate formula.And implement the algorithm on Matlab;（3）Build a simulation model on the HFSS simulation platform.The simulation model is built according to the test layout,including the antenna of the smart watch,the flat phantom and the body simulated tissue fluid,the impedance and output power of the antenna are set,and the specific absorption rate is calculated.Comparing the measured results,the simulation results of the time domain finite difference method and the simulation results of the HFSS platform,the accuracy of calculating the specific absorption rate of the smart watch using the time domain finite difference method is verified;（4）Using the time domain finite difference method simulation model built in this thesis,the factors that affect the test results of the specific absorption rate of smart watches are explored.Recommendations for improvements to the industry-standard smartwatch specific absorption rate test method that should be tested using arm phantoms that are closer to the biometrics of a human arm.The innovations of this thesis are as follows:（1）Build a similar model on the Matlab platform and the HFSS platform according to the smart watch SAR test arrangement mentioned in the standard.The same electrical parameters of the body simulated tissue fluid as in the actual test are added during the simulation.The comparison and analysis of the simulation results and the measured results can prove that the FDTD simulation method has high accuracy.This allows smart watch companies to use the FDTD simulation method during design to calculate the SAR value and reduce the probability of later rectification.（2）By exploring the influencing factors that affect the specific absorption rate of smart watches,we propose improvements to the method of measuring the specific absorption rate of smart watches using flat models and body simulated tissue fluids in the industry standard.Using a model more in line with the human arm and the simulated tissue fluid of the human arm for testing,the smart watch is more accurate than the absorption rate test result,and the harm caused by the electromagnetic radiation of the smart watch to the user is reduced.