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iir Scilab Group Scilab Function iir
NAME
iir - iir digital filter
CALLING SEQUENCE
[hz]=iir(n,ftype,fdesign,frq,delta)
PARAMETERS
n : filter order (pos. integer)
ftype : string specifying the filter type 'lp','hp','bp','sb'
fdesign : string specifying the analog filter design
='butt','cheb1','cheb2','ellip'
frq : 2-vector of discrete cut-off frequencies (i.e., 0<frq<.5).
For lp and hp filters only frq(1) is used. For bp and sb
filters frq(1) is the lower cut-off frequency and frq(2) is the
upper cut-off frequency
delta : 2-vector of error values for cheb1, cheb2, and ellip filters
where only delta(1) is used for cheb1 case, only delta(2) is
used for cheb2 case, and delta(1) and delta(2) are both used
for ellip case. 0<delta(1),delta(2)<1
- for cheb1 filters 1-delta(1)<ripple<1 in passband
- for cheb2 filters 0<ripple<delta(2) in stopband
- for ellip filters 1-delta(1)<ripple<1 in passband and
0<ripple<delta(2) in stopband
DESCRIPTION
function which designs an iir digital filter using analog filter designs.
EXAMPLE
hz=iir(3,'bp','ellip',[.15 .25],[.08 .03]);
[hzm,fr]=frmag(hz,256);
plot2d(fr',hzm')
xtitle('Discrete IIR filter band pass 0.15<fr<0.25 ',' ',' ');
q=poly(0,'q'); //to express the result in terms of the ...
hzd=horner(hz,1/q) //delay operator q=z^-1
SEE ALSO
eqfir, eqiir
AUTHOR
C. B.
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