eqiir

Scilab Function
Last update : 12/01/2004

eqiir - Design of iir filters

### Calling Sequence

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

### Parameters

- `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 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))`

### Examples

    [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')

### See Also

`eqfir` , `iir` ,