eqiir

Design of iir filters

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

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

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).

[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')

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