|MATLAB Function Reference|
Two-dimensional inverse discrete Fourier transform
Y = ifft2(X)
returns the two-dimensional inverse discrete Fourier transform (DFT) of
X, computed with a fast Fourier transform (FFT) algorithm. The result
Y is the same size as
X to see whether it is conjugate symmetric. If so, the computation is faster and the output is real. An
X is conjugate symmetric if
X(i,j) = conj(X(mod(M-i+1, M) + 1, mod(N-j+1, N) + 1)) for each element of
Y = ifft2(X,m,n)
-n inverse fast Fourier transform of matrix
y = ifft2(..., 'symmetric') causes
ifft2 to treat
X as conjugate symmetric. This option is useful when
X is not exactly conjugate symmetric, merely because of round-off error.
y = ifft2(..., 'nonsymmetric') is the same as calling
ifft2(...) without the argument
X to within roundoff error.
The algorithm for
ifft2(X) is the same as the algorithm for
fft2(X), except for a sign change and scale factors of
size(X). The execution time for i
fft2 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
ifft2 supports inputs of data types
single. If you call
ifft2 with the syntax
y = ifft2(X, ...), the output
y has the same data type as the input
freqz in the Signal Processing Toolbox, and:
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