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group(1) Scilab Function group(1)
NAME
group - group delay for digital filter
CALLING SEQUENCE
[tg,fr]=group(npts,a1i,a2i,b1i,b2i)
PARAMETERS
npts : integer : number of points desired in calculation of group
delay
a1i : in coefficient, polynomial, rational polynomial, or cascade
polynomial form this variable is the transfer function of the
filter. In coefficient polynomial form this is a vector of coef-
ficients (see below).
a2i : in coeff poly form this is a vector of coeffs
b1i : in coeff poly form this is a vector of coeffs
b2i : in coeff poly form this is a vector of coeffs
tg : values of group delay evaluated on the grid fr
fr : grid of frequency values where group delay is evaluated
DESCRIPTION
Calculate the group delay of a digital filter with transfer function h(z).
The filter specification can be in coefficient form, polynomial form,
rational polynomial form, cascade polynomial form, or in coefficient poly-
nomial form.
In the coefficient polynomial form the transfer function is formulated by
the following expression
h(z)=prod(a1i+a2i*z+z**2)/prod(b1i+b2i*z+z^2)
EXAMPLE
z=poly(0,'z');
h=z/(z-.5);
[tg,fr]=group(100,h);
plot(fr,tg)
AUTHOR
C. B.
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