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 ;