IFFT

Purpose:

Calculates the Inverse Fast Fourier Transform of a series or series expression with the result in Cartesian (Real/Imaginary) form.

Syntax:

IFFT(series)

series

A series or array.

Returns:

A complex series or table in Cartesian form.

Example:

W1: 1..5

W2: fft(w1)

W3: real(ifft(W2))

W3 contains the series {1, 2, 3, 4, 5}.

Remarks:

FFT and IFFT implement the discrete Fourier transform pair X[k] and x[n] for series x of length N and start index 1 by:

$image\fft01.gif$

A mixed radix algorithm is employed to compute the IFFT, however series with lengths that are a power of 2 will be processed faster than other series. Use the LENGTH function to find out if a series is a power of 2 points long.

Use IFFTP to get magnitude/phase output.

IFFT returns a complex result. Use REAL to obtain the real part.

See DADiSP/FFTXL to optimize the IFFT computation.

References:

Oppenheim and Schafer.

Digital Signal Processing

Prentice Hall, 1975

Digital Signal Processing Committee

Programs for Digital Signal Processing

I.E.E.E. Press, 1979