what is the algorithm behind the fft2 and ifft2 in matlab?

what is the algorithm behind the fft2 and ifft2 in matlab?

Answer 1

[Jan]

The documentation of FFT, FFT2 and FFTW suggests, that the FFTW-library is used and you find more information on http://www.fftw.org.

Answer 2

[mohammed alenazy]

It is this simple

tic; clc; clear all; close all; rng default

sf = 1000; Ts = 1/sf; t = (1:sf)*Ts;

cos_rad = @(theta) cosd(theta/pi*180); sin_rad = @(theta) sind(theta/pi*180);

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x1 = 20*sin(2*pi*70*t)+20*sin(2*pi*50*t)+20*sin(2*pi*30*t); N = length(t);

N1 = length(x1);

X1 = [];

for(K1 = -N1/2:N1/2-1);

C1 = 1*cos_rad(2*pi*K1*t); S1 = 1*sin_rad(2*pi*K1*t);

x1C = x1.*C1; x1S = x1.*S1;

X1C1 = sum(x1C); X1S1 = sum(x1S);

X1C2 = X1C1.^2; X1S2 = X1S1.^2;

X1CS = sqrt(X1C2+X1S2);

X1CS1 = 2*X1CS/N1;

X1 = [X1 X1CS1];

end