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')

See Also

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

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