ifft (Signal Processing Toolbox)

One-dimensional inverse fast Fourier transform.

Syntax

y = ifft(x)
y = ifft(x,n)

Description

ifft computes the inverse Fourier transform of a vector or array. This function implements the inverse transform given by

where W_N = e^-_j^(2p/N) and N = length(x). Note that the series is indexed as n + 1 and k + 1 instead of the usual n and k because MATLAB vectors run from 1 to N instead of from 0 to N-1.

y = ifft(x)

is the inverse Fourier transform of vector x. If x is an array, y is the inverse FFT of each column of the matrix.

y = ifft(x,n)

is the n-point inverse FFT. If the length of x is less than n, ifft pads x with trailing zeros to length n. If the length of x is greater than n, ifft truncates the sequence x. When x is an array, ifft adjusts the length of the columns in the same manner.

The ifft function is part of the standard MATLAB language.

Algorithm

The ifft function is an M-file. The algorithm for ifft is the same as that for fft, except for a sign change and a scale factor of n = length(x). The execution time is fastest when n is a power of two and slowest when n is a large prime.

`fft`	One-dimensional fast Fourier transform.
`fft2`	Two-dimensional fast Fourier transform.
`fftshift`	Rearrange the outputs of `fft` and `fft2`.
`ifft2`	Two-dimensional inverse fast Fourier transform.