2D FFT square function

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T B 2017-9-17

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/357077-2d-fft-square-function

评论： jyoti mundra 2017-11-9

I am trying to perform the 2D FFT on the square function. I have defined the square function using:

if true
deltax = L/N;
deltay = L/N;
x = [-L/2:deltax:L/2-deltax];
y = [-L/2:deltay:L/2-deltay];
[X,Y]=meshgrid(x,y);
func = double(abs(X)<= b/2).*double(abs(Y)<= b/2);
figure;
surf(X,Y,func);
end

This does give the expected answer, namely:

However, when I go further and try and do the FFT using the following code:

if true
  % code
end
deltafx = 1/L;
deltafy = 1/L;
fx = [-1/(2*deltax):deltafx:1/(2*deltax)-deltafx];
fy = [-1/(2*deltay):deltafy:1/(2*deltay)-deltafy];
[FX,FY]=meshgrid(fx,fy);
funcfourier=deltax*deltay*fft2(func);
funcfourier=fftshift(funcfourier);
absfuncfourier=abs(funcfourier);
surf(FX,FY,absfuncfourier);