trans
=====

low-pass to other filter transform



Calling Sequence
~~~~~~~~~~~~~~~~


::

    hzt=trans(hz,tr_type,frq)
    hzt=trans(pd,zd,gd,tr_type,frq)
    [pt,zt,gt]=trans(hz,tr_type,frq)
    [pt,zt,gt]=trans(pd,zd,gd,tr_type,frq)




Arguments
~~~~~~~~~

:hz a single input single output discrete transfer function, the low
  pass filter
: :pd Vector of given filter poles
: :zd Vector of given filter zeros
: :gd scalar: the given filter gain
: :tr_type string, the type of transformation, see description for
  possible values
: :frq 2-vector of discrete cut-off frequencies (i.e., `0<frq<.5`).
  see description for details.
: :hzt transformed filter transfert function.
: :pt vector of transformed filter zeros.
: :zt vector of transformed filter poles.
: :gt a scalar: transformed filter gain.
:



Description
~~~~~~~~~~~

function for transforming standardized low-pass filter given its
poles-zeros_gain representation into one of the following filters:

:tr_type='lp' low pass filter, the cutoff frequency is given by the
  first entry of `frq`, the second one is ignored.
: :tr_type='hp' high pass filter, the cutoff frequency is given by the
  first entry of `frq`, the second one is ignored.
: :tr_type='bp' band pass filter, the frequency range is given by
  `frq(1)` and `frq(2)`.
: :tr_type='sb' stop band filter, the frequency range is given by
  `frq(1)` and `frq(2)`.
:



Used functions
~~~~~~~~~~~~~~

`bilt`_



Examples
~~~~~~~~


::

    `clf`_()
    Hlp=`iir`_(3,'lp','ellip',[0.1 0],[.08 .03]);
    Hbp=trans(Hlp,'bp',[0.01 0.1]);
    Hsb=trans(Hlp,'sb',[0.01 0.1])
    
    `clf`_();`gainplot`_([Hlp;Hbp;Hsb],1d-3,0.48);
    l=`legend`_(['original low pass';'band pass';'stop band']);
    l.legend_location="in_lower_left";




See Also
~~~~~~~~


+ `iir`_ iir digital filter
+ `bilt`_ bilinear or biquadratic transform SISO system given by a
  zero/poles representation


.. _bilt: bilt.html
.. _iir: iir.html