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.TH iir 1 "April 1993" "Scilab Group" "Scilab Function"
.so ../sci.an
.SH NAME
iir - iir digital filter
.SH CALLING SEQUENCE
.nf
[hz]=iir(n,ftype,fdesign,frq,delta)
.fi
.SH PARAMETERS
.TP 10
n
: filter order (pos. integer)
.TP
ftype
: string specifying the filter type
\fV'lp','hp','bp','sb'\fR
.TP
fdesign
: string specifying the analog filter design
\fV='butt','cheb1','cheb2','ellip'\fR
.TP
frq
: 2-vector of discrete cut-off frequencies
(i.e., \fV0<frq<.5\fR). For \fVlp\fR and \fVhp\fR filters only
\fVfrq(1)\fR is used. For \fVbp\fR and \fVsb\fR filters \fVfrq(1)\fR
is the lower cut-off frequency and \fVfrq(2)\fR is
the upper cut-off frequency
.TP
delta
: 2-vector of error values for \fVcheb1, cheb2\fR, and
\fVellip\fR filters where only \fVdelta(1)\fR is used for
\fVcheb1\fR case, only \fVdelta(2)\fR is used for \fVcheb2\fR case,
and \fVdelta(1)\fR and \fVdelta(2)\fR are both used for
\fVellip\fR case. \fV0<delta(1),delta(2)<1\fR
.RS
.TP
-
for \fVcheb1\fR filters \fV1-delta(1)<ripple<1\fR in passband
.TP
-
for \fVcheb2\fR filters \fV0<ripple<delta(2)\fR in stopband
.TP
-
for \fVellip\fR filters \fV1-delta(1)<ripple<1\fR in passband
and \fV0<ripple<delta(2)\fR in stopband
.RE
.SH DESCRIPTION
function which designs an iir digital filter using analog filter designs.
.SH EXAMPLE
.nf
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
.fi
.SH SEE ALSO
eqfir, eqiir
.SH AUTHOR
C. B.
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