trans

Scilab Function
Last update : 19/01/2006

trans - low-pass to other filter transform

### Calling Sequence

  `hzt=trans(hz,tr_type,frq)`
  `hzt=trans(pd,zd,gd,tr_type,frq)`

### Parameters

- `hz` : given fiter transfert function
- `pd` : Vector of given fiter poles
- `zd` : Vector of given fiter zeros
- `gd` : scalar: the given fiter 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` ). For lp and hp filters only frq(1) is used. For bp and sb filters frq(1) is the lower cut-off frequency and frq(2) is the upper cut-off frequency.
- `hzt` : transformed filter transfert function.

### Description

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

low-pass ('lp'), the cutoff frequency is given by the first entry of frq, the second one is ignored

high-pass ('hp'), the cutoff frequency is given by the first entry of frq, the second one is ignored

band-pass ('bp'), the frequency range is given by frq(1) and frq(2)

stop-band ('sb') , the frequency range is given by frq(1) and frq(2).

### Examples

    clf()

    Hlp=iir(3,'lp','ellip',[0.1 0],[.08 .03]);
    subplot(311)
    gainplot(Hlp,1d-3,0.48)
    legend('original low pass')

    Hbp=trans(Hlp,'bp',[0.01 0.1]);
    subplot(312)
    gainplot(Hbp,1d-3,0.48)
    legend('band pass')

    Hsb=trans(Hlp,'sb',[0.01 0.1])
    subplot(313)
    gainplot(Hsb,1d-3,0.48)
    legend('stop band')

### Author

C. Bunks ;