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.

Examples

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.