|MATLAB Function Reference|
Shift zero-frequency component of discrete Fourier transform to center of spectrum
Y = fftshift(X)
rearranges the outputs of
fftn by moving the zero-frequency component to the center of the array. It is useful for visualizing a Fourier transform with the zero-frequency component in the middle of the spectrum.
fftshift(X) swaps the left and right halves of
X. For matrices,
fftshift(X) swaps quadrants one and three of
X with quadrants two and four. For higher-dimensional arrays,
fftshift(X) swaps "half-spaces" of
X along each dimension.
Y = fftshift(X,dim)
fftshift operation along the dimension
For any matrix
sum(sum(X)); the zero-frequency component of the signal is in the upper-left corner of the two-dimensional FFT. For
this zero-frequency component is near the center of the matrix.