zplane - don't the zeros and poles need to be complex?

조회 수: 1 (최근 30일)
Tom 2012년 5월 22일
I'm just getting my head around the zplane function. I'm not how the values of z and p are mapped onto the pole-zero plot. I thought zeros and poles were supposed to have both real and imaginary parts - as these are the axes of the pole-zero plot. But in the examples of zplane code given in the help documentation the z and p values are just single real values. Also, for a 4 pole/zero filter there are 5 values for z and also for p. Shouldn't this be four?
댓글 수: 1이전 댓글 -1개 표시이전 댓글 -1개 숨기기
Matt Fig 2012년 11월 2일
I'm just getting my head around the zplane function. I'm not how the values of z and p are mapped onto the pole-zero plot. I thought zeros and poles were supposed to have both real and imaginary parts - as these are the axes of the pole-zero plot. But in the examples of zplane code given in the help documentation the z and p values are just single real values. Also, for a 4 pole/zero filter there are 5 values for z and also for p. Shouldn't this be four?

댓글을 달려면 로그인하십시오.

채택된 답변

Honglei Chen 2012년 5월 22일
zplane is a little subtle. When B and A are rows, they represent transfer functions. However, if B and A are columns, they are zeros and poles.
Compare
[b,a] = ellip(4,.5,20,.6);
zplane(b,a)
zplane(roots(b),roots(a))
댓글 수: 6이전 댓글 4개 표시이전 댓글 4개 숨기기
Tom 2012년 5월 24일
great thanks :)
Honglei Chen 2012년 5월 24일
Hi Tom, in your code, b and a are coefficients. So if you want to use zplane, you need to keep them in the row form and zplane will automatically calculate zeros and poles for you and display in the figure.
On the other hand, if you want to pass in column vectors, then zplane treat them as just zeros and poles. In this case, you need to compute zeros and poles yourself before passing it into the function. So you need to do zplane(roots(b),roots(a)).
HTH

댓글을 달려면 로그인하십시오.

카테고리

Help CenterFile Exchange에서 Digital Filter Analysis에 대해 자세히 알아보기

Community Treasure Hunt

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

Start Hunting!

Translated by