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eqiir Scilab Group Scilab Function eqiir
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eqiir - Design of iir filters
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[cells,fact,zzeros,zpoles]=eqiir(ftype,approx,om,deltap,deltas)
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ftype : filter type ('lp','hp','sb','bp')
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approx : design approximation ('butt','cheb1','cheb2','ellip')
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om : 4-vector of cutoff frequencies (in radians)
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om=[om1,om2,om3,om4], 0 <= om1 <= om2 <= om3 <= om4 <= pi.
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When ftype='lp' or 'hp', om3 and om4 are not used and may be
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deltap : ripple in the passband. 0<= deltap <=1
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deltas : ripple in the stopband. 0<= deltas <=1
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cells : realization of the filter as second order cells
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fact : normalization constant
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zzeros : zeros in the z-domain
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zpoles : poles in the z-domain
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Design of iir filter interface with eqiir (syredi)
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The filter obtained is h(z)=fact*product of the elements of cells.
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That is hz=fact*prod(cells(2))./prod(cells(3))
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[cells,fact,zzeros,zpoles]=...
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eqiir('lp','ellip',[2*%pi/10,4*%pi/10],0.02,0.001)
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transfer=fact*poly(zzeros,'z')/poly(zpoles,'z')