confused abt z and z(-1) in matlab

9 views (last 30 days)
moonman
moonman on 13 Nov 2011
Lets suppose i am having one transfer function as
H(z)= 1-2z/(1+3z)
and the other is
G(z) = 1-2z(-1)/ [1+3z(-1)] //Now inverse is used
If i want to take the transfer fucntion in matlab for further pole zero map, how i will tell matlab that it is z in my TF or z(-1)
  2 Comments
Walter Roberson
Walter Roberson on 13 Nov 2011
Is that really z multiplied by negative one? Or is it z raised to the power of negative 1, z^(-1), which is 1/z ?
moonman
moonman on 13 Nov 2011
It is z raise to power -1
yes 1/z...
H(z) contaiins all z
G(z) contains all z(inverse power)

Sign in to comment.

Accepted Answer

Naz
Naz on 13 Nov 2011
You can take your H(z) and divide by z. So you will have: z^(-1)-2 / z^(-1)+3. Now you can create two vectors containing zeros and poles:
B=[-2 1];
A=[3 1];
zplane(B,A)
If you have function with (all) negative powers, than the last coefficient is for the most negative power and the first coeff is a constant. In case of all positive coeff. you just inverse the order (constant is last).

More Answers (2)

moonman
moonman on 13 Nov 2011
Is there any way i can directly use H(z) for calculations
  2 Comments
Walter Roberson
Walter Roberson on 13 Nov 2011
Not without the symbolic toolbox.
Naz
Naz on 13 Nov 2011
I dont really understand what you are trying to do. Please, be more specific.

Sign in to comment.


moonman
moonman on 13 Nov 2011
I just want to ask that some times we are having transfer function which is expressed in z and some times it is expressed in z(inverse) format
how to handle both I am sure both cannot be handled by one command of matlab like tf is used with z(inverse)

Tags

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!