SHAH Discrete Shah-distribution
Usage: f=shah(L,a);
SHAH(L,a) computes the discrete, normalized Shah-distribution of
length L with a distance of a between the spikes.
The Shah distribution is defined by
f(n*a+1)=1/sqrt(L/a)
for integer n, otherwise f is zero.
This is also known as an impulse train or as the comb function, because
the shape of the function resembles a comb. It is the sum of unit
impulses ('diracs') with the distance a.
If a divides L, then the DFT of SHAH(L,a) is SHAH(L,L/a).
The Shah function has an extremely bad time-frequency localization.
It does not generate a Gabor frame for any L and a.
Examples:
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A simple spectrogram of the Shah function (includes the negative
frequencies to display the whole TF-plane):
sgram(shah(256,16),'dynrange',80,'nf')
Package: ltfat