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Aide Scilab >> Traitement du Signal > iir


iir digital filter

Calling Sequence




positive number witn inteher value, the filter order.


string specifying the filter type, the possible values are: 'lp' for low-pass,'hp' for high pass,'bp' for band pass and 'sb' for stop band.


string specifying the analog filter design, the possible values are: 'butt', 'cheb1', 'cheb2' and 'ellip'


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


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


function which designs an iir digital filter using analog filter designs and bilinear transformation .


hz=iir(3,'bp','ellip',[.15 .25],[.08 .03]);
xtitle('Discrete IIR filter band pass  0.15&lt;fr&lt;0.25 ',' ',' ');
q=poly(0,'q');     //to express the result in terms of the delay operator q=z^-1

See Also

  • eqfir — minimax approximation of FIR filter
  • eqiir — Design of iir filters
  • analpf — create analog low-pass filter
  • bilt — bilinear or biquadratic transform SISO system given by a zero/poles representation


Carey Bunks

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Last updated:
Wed Oct 05 12:10:56 CEST 2011