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.TH analpf 1 "April 1993" "Scilab Group" "Scilab Function"
.so ../sci.an
.SH NAME
analpf - create analog low-pass filter
.SH CALLING SEQUENCE
.nf
[hs,pols,zers,gain]=analpf(n,fdesign,rp,omega)
.fi
.SH PARAMETERS
.TP 10
n
: positive integer : filter order
.TP
fdesign
: string : filter design method : \fV'butt'\fR or \fV'cheb1'\fR or \fV'cheb2'\fR or \fV'ellip'\fR
.TP
rp
: 2-vector of error values for cheb1, cheb2 and
ellip filters where only \fVrp(1)\fR is used for
cheb1 case, only \fVrp(2)\fR is used for cheb2 case, and
\fVrp(1)\fR and \fVrp(2)\fR are both used for ellip case.
\fV0<rp(1),rp(2)<1\fR
.RS
.TP
-
for cheb1 filters \fV1-rp(1)<ripple<1\fR in passband
.TP
-
for cheb2 filters \fV0<ripple<rp(2)\fR in stopband
.TP
-
for ellip filters \fV1-rp(1)<ripple<1\fR in passband
\fV0<ripple<rp(2)\fR in stopband
.RE
.TP
omega
: cut-off frequency of low-pass filter in Hertz
.TP
hs
: rational polynomial transfer function
.TP
pols
: poles of transfer function
.TP
zers
: zeros of transfer function
.TP
gain
: gain of transfer function
.SH DESCRIPTION
Creates analog low-pass filter with cut-off frequency at omega.
.LP
\fVhs=gain*poly(zers,'s')/poly(pols,'s')\fR
.SH EXAMPLE
.nf
//Evaluate magnitude response of continuous-time system
hs=analpf(4,'cheb1',[.1 0],5)
fr=0:.1:15;
hf=freq(hs(2),hs(3),%i*fr);
hm=abs(hf);
plot(fr,hm)
.fi
.SH AUTHOR
C. B.
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