analpf - create analog low-pass filter

Calling Sequence

[hs,pols,zers,gain]=analpf(n,fdesign,rp,omega)

Parameters

• n : positive integer : filter order
• fdesign : string : filter design method : 'butt' or 'cheb1' or 'cheb2' or 'ellip'
• rp : 2-vector of error values for cheb1, cheb2 and ellip filters where only rp(1) is used for cheb1 case, only rp(2) is used for cheb2 case, and rp(1) and rp(2) are both used for ellip case. 0<rp(1),rp(2)<1
• - for cheb1 filters 1-rp(1)<ripple<1 in passband
• - for cheb2 filters 0<ripple<rp(2) in stopband
• - for ellip filters 1-rp(1)<ripple<1 in passband 0<ripple<rp(2) in stopband
• omega : cut-off frequency of low-pass filter in Hertz
• hs : rational polynomial transfer function
• pols : poles of transfer function
• zers : zeros of transfer function
• gain : gain of transfer function

Description

Creates analog low-pass filter with cut-off frequency at omega.

hs=gain*poly(zers,'s')/poly(pols,'s')

Examples

//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)
 

Author

C. B.