|MATLAB Function Reference|
Inverse discrete Fourier transform
y = ifft(X)
returns the inverse discrete Fourier transform (DFT) of vector
X, computed with a fast Fourier transform (FFT) algorithm. If
X is a matrix,
ifft returns the inverse DFT of each column of the matrix.
X to see whether vectors in
X along the active dimension are conjugate symmetric. If so, the computation is faster and the output is real. An
x is conjugate symmetric if
x(i) = conj(x(mod(N-i+1,N)+1)) for each element of
X is a multidimensional array,
ifft operates on the first non-singleton dimension.
y = ifft(X,n)
n-point inverse DFT of vector
y = ifft(X,,dim)
y = ifft(X,n,dim) return the inverse DFT of
X across the dimension
y = ifft(..., 'symmetric') causes
ifft to treat
X as conjugate symmetric along the active dimension. This option is useful when
X is not exactly conjugate symmetric, merely because of round-off error.
y = ifft(..., 'nonsymmetric') is the same as calling
ifft(...) without the argument
X to within roundoff error.
The algorithm for
ifft(X) is the same as the algorithm for
fft(X), except for a sign change and a scale factor of
length(X). As for
fft, the execution time for i
fft depends on the length of the transform. It is fastest for powers of two. It is almost as fast for lengths that have only small prime factors. It is typically several times slower for lengths that are prime or which have large prime factors.
You might be able to increase the speed of |
Data Type Support
ifft supports inputs of data types
single. If you call
ifft with the syntax
y = ifft(X, ...), the output
y has the same data type as the input
freqz, in the Signal Processing Toolbox
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