Matlab fftshift

1. What does Fftshift in Matlab do?
2. What is the difference between fft and Fftshift?
3. Should I use Fftshift?
4. How do you shift frequency in Matlab?

What does Fftshift in Matlab do?

Y = fftshift( X ) rearranges a Fourier transform X by shifting the zero-frequency component to the center of the array. If X is a vector, then fftshift swaps the left and right halves of X . If X is a matrix, then fftshift swaps the first quadrant of X with the third, and the second quadrant with the fourth.

What is the difference between fft and Fftshift?

fft computes the discrete Fourier transform and by definition the output is complex. fftshift doesn't compute anything except swaping the position of the samples, so if your input is real, you get real output.

Should I use Fftshift?

It depends on what you are going to do with the transformed data. If you don't perform an fftshift before transforming, the fft result will have every other value multiplied by -1. This doesn't matter if you plan to view the magnitude or magnitude squared of the result.

How do you shift frequency in Matlab?

In Matlab you can use the fftshift() command. It will rearrange the samples so that the frequency range is between −fs/2 and fs/2.