A list,

The use frequency of mobile phone is 800-1800 MHz. When the microwave radiated by mobile phone antenna spreads from the air and collids with living surfaces, the propagation conditions change. Microwaves reflect, refract and absorb the surface of an organism, some of which enter the organism. At this point, if traveling in the right direction through the body, total reflection occurs, forming a standing wave that allows the body to absorb maximum energy. Due to the high frequency and short wavelength of mobile phone microwave radiation, when it acts on living body, it is not a continuous field energy, but a pulse wave energy, so the impact on living body becomes greater. To keep a phone online at all times, it needs to contact a base station with electromagnetic waves, further increasing the amount of time it takes for the body to absorb them. In essence, a mobile phone can be thought of as a low-power wireless transceiver that emits high-frequency radio waves that can adversely affect human health. Since these mobile terminals are often used close to the human brain, this is an issue worth considering. Long-term use of mobile phones will cause a certain degree of damage to the eyes, ears and other important organs, without the protection of the brain. There is such a phenomenon in life. When we sit in front of the computer, when the mobile phone rings, there will be a horizontal line on the electronic LCD screen flashing, and the speaker will also make a “drop” interference sound, indicating that the absorption of electromagnetic waves is the LCD and speaker, but the human body is not directly felt. This effect is called nonthermal. Infrared ray can make the person feel feverish, call heat effect. Heat effect is to show human body absorbs radiation energy below electromagnetic radiation, transform into heat energy inside the body, heat local organization, produce biological effect. Under the action of electric field, the body’s positive and negative charges move in opposite directions and become polarized. In the process of alternating polarization and orientation, collision and friction generate heat and electrolytes are also present in the body. Internal ions tend to move in response to an electric field, and when the frequency of the electromagnetic field is high, these ions vibrate in the equilibrium position, converting electrical energy into heat energy. Electromagnetic fields also create local eddies in the body that generate heat. Non-thermal effects can cause headaches, memory loss and potential biological damage for people who use their phones regularly. The measurement standard of mobile phone radiation mainly includes power density standard and specific absorption rate (SAR) standard. This design will be studied using the specific absorption rate standard.

2 Introduction to the Finite difference Time domain method (FDTD) The finite difference time domain method (FDTD) was published in AP by KSYee in 1966 and later became known as The Yee Grid Space Discretization method. This method was first introduced in the 1960s and began to attract attention. In the 1970 s. After the 1980s, it was gradually accepted and began to develop in the field of electromagnetic computing. In this era, this approach has entered a period of vigorous development. At present, the applications of FDTD method in electromagnetic scattering, electromagnetic compatibility, antenna and biological electromagnetic problems emerge one after another. The core idea of finite-difference time-domain method is to transform maxwell’s curl equation with time variable into differential form to simulate the time-domain response of electron pulse and the ideal conductor action. Frogfrog algorithm – the electric and magnetic fields in the electric and magnetic fields are updated in the time domain to simulate the changes of the electromagnetic field, to achieve the purpose of numerical calculation. In this way, geometric parameters, material parameters, computational accuracy, computational complexity and computational stability of the object should be considered. Its advantage is that it can directly simulate the distribution of field and has high precision. This is one of the commonly used methods in numerical simulation.

This design first introduces the impact of mobile communication terminals on human body, research methods and measurement standards. Then the finite difference time domain (FDTD) theory and SAR standard, simulation and simulation are introduced in detail, and then the penetration depth of electromagnetic wave to medium is introduced. A method to protect mobile phone radiation is proposed. Finally, the design is summarized, and the corresponding protection measures are put forward.

Ii. Source code

clear

%***********************************************************************
%     Fundamental constants
%***********************************************************************

cc=2.99792458 e8;            %speed of light in freeMuz = space at the speed of light4.0*pi*1.0 e-7;          %permeability of freeSpace Free space permeability EPSZ =1.0/(cc*cc*muz);       %permittivity of freeSpace Free space dielectric constant freq=1.0 e+9; %frequency of source dispatching lambda=cc/freq; % Wavelength of Source excitation Omega =2.0*pi*freq; Angular frequency % % * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * % Grid parameters Grid parameters %*********************************************************************** ie=200; %number of grid cells in x-direction ib= IE +1;

dx=lambda/20.0;             %space increment of 1-D lattice
dt=dx/cc;                   %time step
omegadt=omega*dt;

nmax=round(12.0 e-9/dt);     %total number of time steps

%***********************************************************************
%     Material parameters
%***********************************************************************

eps=1.0;
sig=5.0 e-3;

%***********************************************************************
%     Updating coefficients forSpace region with nonpermeable Media Update the coefficients of spatial regions with impermeable media %*********************************************************************** scfact=dt/muz/dx; ca=(1.0-(dt*sig)/(2.0*epsz*eps))/(1.0+(dt*sig)/(2.0*epsz*eps));
cb=scfact*(dt/epsz/eps/dx)/(1.0+(dt*sig)/(2.0*epsz*eps));

%***********************************************************************
%     Field arrays
%***********************************************************************

ez(1:ib)=0.0;
hy(1:ie)=0.0;

%***********************************************************************
%     Movie initialization
%***********************************************************************

x=linspace(dx,ie*dx,ie);

subplot(2.1.1),plot(x,ez(1:ie)/scfact,'r'),axis([0 3 - 1 1]);
ylabel('EZ');

subplot(2.1.2),plot(x,hy,'b'),axis([0 3 3.0 e-3 3.0 e-3]);
xlabel('x (meters)'); ylabel('HY');

rect=get(gcf,'Position');
rect(1:2) = [0 0];

M=moviein(nmax/2,gcf,rect); %*********************************************************************** % BEGIN TIME-STEPPING LOOP % * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *for n=1: nmax % * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * % Update electric fields, electric fields %*********************************************************************** ez(1)=scfact*sin(omegadt*n);

rbc=ez(ie);
ez(2:ie)=ca*ez(2:ie)+cb*(hy(2:ie)-hy(1:ie- 1));
ez(ib)=rbc;

%***********************************************************************
%     Update magnetic fields
%***********************************************************************

hy(1:ie)=hy(1:ie)+ez(2:ib)-ez(1:ie); % * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * %3-D FDTD code with PML absorbing boundary conditions
%***********************************************************************
function fdtd3D

clear
clc
%***********************************************************************
%     Fundamental constants
%***********************************************************************
cc=2.99792458 e8;            %speed of light in free space
muz=4.0*pi*1.0 e-7;          %permeability of free space
epsz=1.0/(cc*cc*muz);       %permittivity of free space
etaz=sqrt(muz/epsz);

freq=9e8;
lambda=cc/freq;
omega=2.0*pi*freq;

%***********************************************************************
%     Grid parameters
%***********************************************************************

ie=80;           %number of grid cells in x-direction
if mod(ie,2)= =0
    ie=ie+1;
end       %Force it to be a odd integer!
je=80;            %number of grid cells in y-direction
if mod(je,2)= =0
    je=je+1;
end       %Force it to be a odd integer!
ke=80;             %number of grid cells in z-direction
if mod(ke,2)= =0
    ke=ke+1;
end       %Force it to be a odd integer!

ib=ie+1;
jb=je+1;
kb=ke+1;

is=45;          %location of  hard source in x axis
js=25;          %location of  hard source in y axis
ks=50;          %location of  hard source in z axis


ds=lambda/20;        %space increment of square lattice
dt=ds/(2.0*cc);   %time step

nmax=800;        

iebc=8;           %thickness of left and right PML region
jebc=8;           %thickness of front and back PML region
kebc=8;           %thickness of bottom and top PML region
ibbc=iebc+1;
jbbc=jebc+1;
kbbc=kebc+1;
iefbc=ie+2*iebc;
jefbc=je+2*jebc;
kefbc=ke+2*kebc;
ibfbc=iefbc+1;
jbfbc=jefbc+1;
kbfbc=kefbc+1;

rmax=1.0 e-7;
orderbc=2;

%***********************************************************************
%     Material parameters
%***********************************************************************

media=2;

eps=[1.0 1.0];
sig=[0.0 1.0 e+7];
mur=[1.0 1.0];
sim=[0.0 0.0];

ds = ds/sqrt(eps(1)*mur(1));

%***********************************************************************
%     Wave excitation
%***********************************************************************

source=zeros(1,nmax);

for n=1:nmax
    source(n)=15.5*sin(omega*n*dt);
end

%***********************************************************************
%     Field arrays
%***********************************************************************

ex=zeros(ie,jb,kb);           %fields in main grid
ey=zeros(ib,je,kb);
ez=zeros(ib,jb,ke);

hx=zeros(ib,je,ke);
hy=zeros(ie,jb,ke);
hz=zeros(ie,je,kb);


exybcf=zeros(iefbc,jebc,kbfbc);   %fields in front PML region
exzbcf=zeros(iefbc,jebc,kbfbc);
eyzbcf=zeros(ibfbc,jebc,kbfbc);
eyxbcf=zeros(ibfbc,jebc,kbfbc);
ezxbcf=zeros(ibfbc,jebc,kefbc);
ezybcf=zeros(ibfbc,jebc,kefbc);

hxybcf=zeros(ibfbc,jebc,kefbc);
hxzbcf=zeros(ibfbc,jebc,kefbc);
hyzbcf=zeros(iefbc,jebc,kefbc);
hyxbcf=zeros(iefbc,jebc,kefbc);
hzxbcf=zeros(iefbc,jebc,kbfbc);
hzybcf=zeros(iefbc,jebc,kbfbc);


exybcb=zeros(iefbc,jebc,kbfbc);   %fields in back PML region
exzbcb=zeros(iefbc,jebc,kbfbc);
eyzbcb=zeros(ibfbc,jebc,kbfbc);
eyxbcb=zeros(ibfbc,jebc,kbfbc);
ezxbcb=zeros(ibfbc,jebc,kefbc);
ezybcb=zeros(ibfbc,jebc,kefbc);

hxybcb=zeros(ibfbc,jebc,kefbc);
hxzbcb=zeros(ibfbc,jebc,kefbc);
hyzbcb=zeros(iefbc,jebc,kefbc);
hyxbcb=zeros(iefbc,jebc,kefbc);
hzxbcb=zeros(iefbc,jebc,kbfbc);
hzybcb=zeros(iefbc,jebc,kbfbc);


exybcl=zeros(iebc,jb,kbfbc);      %fields in left PML region
exzbcl=zeros(iebc,jb,kbfbc);
eyzbcl=zeros(iebc,je,kbfbc);
eyxbcl=zeros(iebc,je,kbfbc);
ezxbcl=zeros(iebc,jb,kefbc);
ezybcl=zeros(iebc,jb,kefbc);

hxybcl=zeros(iebc,je,kefbc);
hxzbcl=zeros(iebc,je,kefbc);
hyzbcl=zeros(iebc,jb,kefbc);
hyxbcl=zeros(iebc,jb,kefbc);
hzxbcl=zeros(iebc,je,kbfbc);
hzybcl=zeros(iebc,je,kbfbc);


exybcr=zeros(iebc,jb,kbfbc);      %fields in right PML region
exzbcr=zeros(iebc,jb,kbfbc);
eyzbcr=zeros(iebc,je,kbfbc);
eyxbcr=zeros(iebc,je,kbfbc);
ezxbcr=zeros(iebc,jb,kefbc);
ezybcr=zeros(iebc,jb,kefbc);

hxybcr=zeros(iebc,je,kefbc);
hxzbcr=zeros(iebc,je,kefbc);
hyzbcr=zeros(iebc,jb,kefbc);
hyxbcr=zeros(iebc,jb,kefbc);
hzxbcr=zeros(iebc,je,kbfbc);
hzybcr=zeros(iebc,je,kbfbc);


exybcd=zeros(ie,jb,kebc);           %fields in bottom PML region
exzbcd=zeros(ie,jb,kebc);
eyzbcd=zeros(ib,je,kebc);
eyxbcd=zeros(ib,je,kebc);
ezxbcd=zeros(ib,jb,kebc);
ezybcd=zeros(ib,jb,kebc);

hxybcd=zeros(ib,je,kebc);
hxzbcd=zeros(ib,je,kebc);
hyzbcd=zeros(ie,jb,kebc);
hyxbcd=zeros(ie,jb,kebc);
hzybcd=zeros(ie,je,kebc);
hzxbcd=zeros(ie,je,kebc);


exybct=zeros(ie,jb,kebc);          %fields in top PML region
exzbct=zeros(ie,jb,kebc);
eyzbct=zeros(ib,je,kebc);
eyxbct=zeros(ib,je,kebc);
ezxbct=zeros(ib,jb,kebc);
ezybct=zeros(ib,jb,kebc);
Copy the code

3. Operation results

Fourth, note

Version: 2014 a