fast_fourier_transform.m

Multi-Layer optical filter. FDTD Simulation comparing with analytic methods.

%%%%%%%%%%%%%%%%%%%%%%% In The Name of God %%%%%%%%%%%%%%%%%%%%%%
% 
% Numerical Method in Electromagnetic
% Dr. M.S Abrishamian
% 
% Mohsen Bahrami Panah        8600374                4/11/86
% 
% Problem 8 ---------- *** Multi-Layers Optical Filter ***
% 
% note : This function calculate the Fourier transform of signal ERS & ET.

function[ff,FES,FER,FET]=FAST_FOURIER_TRANSFORM(DT,S,ERS,ET)


for P=1:S
    ES(P)=ERS(P);
end
for W=S+1:1000
    ER(W)=ERS(W);
end
LL = length((ER)*2);
MM = log2(LL);
if MM-fix(MM)>0
    MM = MM+1;
end
NFFT = 2^round(MM);
FES = fft(ES,NFFT);
FER = fft(ER,NFFT);
FET = fft(ET,NFFT);
FES = abs(FES).^2/NFFT;
FER = abs(FER).^2/NFFT;
FET = abs(FET).^2/NFFT;
ff = (0:NFFT-1)/NFFT/DT;