【电磁波】 基于matlab 一维FDTD方法电磁波传播仿真【含Matlab源码 3868期】.zip

%*********************************************************************** % 1-D FDTD code with simple radiation boundary conditions %*********************************************************************** % % % % This MATLAB M-file implements the finite-difference time-domain % solution of Maxwell's curl equations over a one-dimensional space % lattice comprised of uniform grid cells. % % To illustrate the algorithm, a sinusoidal wave (1GHz) propagating % in a nonpermeable lossy medium (epsr=1.0, sigma=5.0e-3 S/m) is % modeled. The simplified finite difference system for nonpermeable % media (discussed in Section 3.6.6 of the text) is implemented. % % The grid resolution (dx = 1.5 cm) is chosen to provide 20 % samples per wavelength. The Courant factor S=c*dt/dx is set to % the stability limit: S=1. In 1-D, this is the "magic time step." % % The computational domain is truncated using the simplest radiation % boundary condition for wave propagation in free space: % % Ez(imax,n+1) = Ez(imax-1,n) % % To execute this M-file, type "fdtd1D" at the MATLAB prompt. % This M-file displays the FDTD-computed Ez and Hy fields at every % time step, and records those frames in a movie matrix, M, which is % played at the end of the simulation using the "movie" command. % %*********************************************************************** clear %*********************************************************************** % Fundamental constants %*********************************************************************** cc=2.99792458e8; %speed of light in free space muz=4.0*pi*1.0e-7; %permeability of free space epsz=1.0/(cc*cc*muz); %permittivity of free space freq=1.0e+9; %frequency of source excitation lambda=cc/freq; %wavelength of source excitation omega=2.0*pi*freq; %*********************************************************************** % 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(12.0e-9/dt); %total number of time steps %*********************************************************************** % Material parameters %*********************************************************************** eps=1.0; sig=5.0e-3; %*********************************************************************** % Updating coefficients for space region with nonpermeable 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 -3.0e-3 3.0e-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 %*********************************************************************** 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); %*********************************************************************** % Visualize fields %*********************************************************************** if mod(n,2)==0; rtime=num2str(round(n*dt/1.0e-9)); subplot(2,1,1),plot(x,ez(1:ie)/scfact,'r'),axis([0 3 -1 1]); title(['time = ',rtime,' ns']); ylabel('EZ'); subplot(2,1,2),plot(x,hy,'b'),axis([0 3 -3.0e-3 3.0e-3]); title(['time = ',rtime,' ns']); xlabel('x (meters)');ylabel('HY'); M(:,n/2)=getframe(gcf,rect); end %*********************************************************************** % END TIME-STEPPING LOOP %*********************************************************************** end movie(gcf,M,0,10,rect);