eqiir

eqiir — Design of iir filters

Calling sequence

[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 interface with eqiir (syredi)

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

That is hz=fact*prod(cells(2))./prod(cells(3))



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