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fftrealinv

void fftrealinv( int * x, int N, int * blockexp );

Description

Computes the 2N-point real sequence corresponding to the N-point, positive-frequency complex spectrum in array x. The N-point, positive-frequency spectrum contained in array x is replaced with its corresponding 2N-point real sequence. The value of blockexp is increased by 1 each time array x has to be scaled, to avoid arithmetic overflow. The value of blockexp is also decreased by log₂N to include the 1/N factor in the definition of the inverse DFT.

The function expects to find the real part of the fmax term in the imaginary part of the zero-frequency X[0] term (stored x[1]).

The 2N-point real sequence is stored in natural order. The zeroth element of the sequence is stored in x[0], the first element in x[1], and the kth element in x[k].

N must be a power of 2 and between 4 and 1024. An invalid N causes a RANGE exception.

Parameters

x

Pointer to N-element array of complex fractions.

N

Number of complex elements in array x.

blockexp

Pointer to integer block exponent.

Library

FFT.LIB

See also

fftcplx, fftcplxinv, fftreal, hanncplx, hannreal, powerspectrum