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


.. _syredi: syredi.html
.. _eqfir: eqfir.html
.. _iir: iir.html