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hannreal

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

Description

Convolves an N-point positive-frequency complex spectrum with the three-point Hann kernel. The function produces the same results as would be obtained by multiplying the corresponding time sequence by the Hann raised-cosine window.

The zero-crossing width of the main lobe produced by the Hann window is 4 DFT bins. The adjacent sidelobes are 32 db below the main lobe. Sidelobes decay at an asymptotic rate of 18 db per octave.

The imaginary part of the dc term (stored in x[1]) is considered to be the real part of the fmax term. The dc and fmax spectral components take part in the convolution along with the other spectral components. The real part of fmax component affects the real part of the X[N-1] component (and vice versa), and should not arbitrarily be set to zero unless these components are unimportant.

Parameters

x

Pointer to N-element array of complex fractions.

N

Number of complex elements in array x.

blockexp

Pointer to integer block exponent.

Return value

None. The filtered spectrum replaces the original spectrum.

Library

FFT.LIB

See also

fftcplx, fftcplxinv, fftreal, fftrealinv, hanncplx, powerspectrum