Evolution of an electromagnetic pulse

Beijing Institute of Technology | Ming-Jian Li

The following MATLAB code is a companion code for the course on Artificial Intelligence and Simulation Science. It is designed to calculate the evolution process of an electromagnetic pulse using the Finite-Difference Time-Domain (FDTD) method.

​x
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% 1D FDTD simulation with pulse
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clear;
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ke = 100;
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% Position of the source
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ks = 1;
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% ks = ke / 2;
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% Number of time steps
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nsteps = 2000;
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% Cell size and time stepping
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c0 = 3.e8;
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dx = 0.01;
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dt = dx / (2 .* c0);
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% Constants
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cc = c0 * dt / dx;
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% Initialize vectors
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ex = zeros(1, ke);
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hy = zeros(1, ke);
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% Gaussian pulse
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t0 = 20;
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spread = 8;
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% Gaussian signal
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for t = 1:nsteps
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    time(t) = t;
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    ex_source(t) = exp(- .5 * ((t - t0) / spread) ^ 2);
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end
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plot(time,ex_source)
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% Start loop
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M = moviein(nsteps);
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for t = 1:nsteps
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    % E field loop
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    for k = 2:ke - 1
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        ex(k) = ex(k) + cc * (hy(k - 1) - hy(k));
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    end
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    % Source
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    ex(ks) = exp(- .5 * ((t - t0) / spread) ^ 2);
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    % H field loop
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    for k = 1:ke - 1
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        hy(k) = hy(k) + cc * (ex(k) - ex(k + 1));
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    end
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    plot(ex); axis([1 ke -2 2]);
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    % plot(hy); axis([1 ke -2 2]);
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    M(:, t) = getframe;
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end

The result is as follows.