Research On High Precision Simulation Technology Of Specific Absorption Rate Of Human Head Mode

Electromagnetic radiation can be described as the phenomenon that energy moves and propagates in space when wave or particle is accelerated by electric field.With the development of communication technology and the increase of mobile communication users,especially the promotion of 5G communication technology,the influence of electromagnetic radiation of mobile phone on human health has become a topic of general interest.As a measure of electromagnetic radiation,the specific absorption rate can reflect the electromagnetic power absorbed or consumed by human tissues of unit mass,which is of great significance to the study of the influence of electromagnetic radiation on human body.In order to test the influence of electromagnetic radiation of mobile phone on the electromagnetic model of human head,we have finished the research work in this thesis as follows.（1）The basic principle of finite difference time domain（FDTD）method is analyzed for solving electromagnetic field equations.By using the distribution of electric-and magnetic-fields in Yee cell,the recurrence formulas of electric field and magnetic field along each axial direction are derived.At the same time,it summarizes the basic steps of electromagnetic modeling using the basic principle of the FDTD,and deduces the process of calculating the specific absorption rate（SAR）value using FDTD,which lays a theoretical basis for the subsequent modeling and simulation.（2）Based on the basic principle of microstrip antenna design and the basic theory of improving the antenna gain and directivity,two microstrip antenna structures for 5G millimeter wave with a central working frequency of 28GHz are designed.One is the traditional microstrip monopole planar antenna structure,which has a small overall size and omnidirectional radiation characteristics.The working bandwidth of 6.5GHz has certain ultra wideband characteristics.The other is The antenna structure of the dipole,and by adding reflectors with band-pass and band stop characteristics to the structure of the antenna,to suppress the side lobe level of the antenna,so as to improve the gain of the antenna,so that it has a higher radiation efficiency in a longer distance.Through the simulation of the electromagnetic simulation software,the S₁₁ of the antenna in the working bandwidth of 28GHz can reach below-10d B,with good performance Characteristics.（3）Due to the high frequency of millimeter wave,the accuracy of grid step is required to be higher in the FDTD electromagnetic calculation process,so it is necessary to optimize the accuracy of the electromagnetic model of the human head to analyze the influence of the human head by the electromagnetic model under the high frequency electromagnetic radiation.In the process of modeling,image smoothing and coordinate system stretching are used to optimize the mesh precision of human head model,so that it can better carry out simulation test and experimental results analysis in the frequency range of millimeter wave.（4）The millimeter wave antenna is placed in the electromagnetic model structure of mobile phone,and the electromagnetic model of specific absorption rate of high-precision electromagnetic model of human head is simulated and tested by CST software.Through observing the electric field distribution on the surface of electromagnetic model of human head,the local peak value of its SAR value is deduced,and compared with the limit value proposed by the relevant agencies,it is proved that the millimeter wave of 28GHz is harmless for the human body.