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Aide Scilab >> Traitement du Signal > eqiir

eqiir

Design of iir filters

Calling Sequence

`[cells,fact,zzeros,zpoles]=eqiir(ftype,approx,om,deltap,deltas)`

Arguments

ftype

filter type (`'lp','hp','sb','bp'`)

approx

design approximation (`'butt','cheb1','cheb2','ellip'`)

om

4-vector of cutoff frequencies (in radians) `om=[om1,om2,om3,om4]`, ```0 <= om1 <= om2 <= om3 <= om4 <= pi```. When `ftype`='lp' or 'hp', `om3` and `om4` are not used and may be set to 0.

deltap

ripple in the passband. ```0<= deltap <=1```

deltas

ripple in the stopband. ```0<= deltas <=1```

cells

realization of the filter as second order cells

fact

normalization constant

zzeros

zeros in the z-domain

zpoles

poles in the z-domain

Description

Design of iir filter based on syredi.

The filter obtained is `h(z)=fact`*product of the elements of `cells`.

That is `hz=fact*prod(cells.num)./prod(cells.den).`

Examples

```[cells,fact,zzeros,zpoles]=eqiir('lp','ellip',[2*%pi/10,4*%pi/10],0.02,0.001)
h=fact*poly(zzeros,'z')/poly(zpoles,'z')```

• eqfir — minimax approximation of FIR filter
• iir — iir digital filter
• syredi — Design of iir filters, syredi code interface