FFTSHIFT

Purpose:

Shifts a 1D or 2D FFT so the 0 frequency is the midpoint.

Syntax:

FFTSHIFT(series)

series

-

Any series or multi-column table.

Returns:

A series or array.

Example:

W1: {1, 2, 3, 2, 1}

W2: fft(W1)

W3: fftshift(W2)

 

The zero frequency (i.e. DC) value of W2 is the first point. The zero frequency of W3 is the 3rd point and appears in the middle of the resulting graph.

Example:

W1: gcos(100,.01,10)

W2: fftp(w1, 8*1024)

W3: fftshift(w2)

 

image\fftshiftpic.gif

 

The frequency peaks in W3 appear at +- 10 Hertz.

Remarks:

FFTSHIFT also works on 2D FFT array.

 

See IFFTSHIFT to undo the shift produced by FFTSHIFT.

See Also:

CIRCSHIFT

FFT

FFT2

IFFTSHIFT