| Author |
Message |
edafisher
Joined: 25 Dec 2004
Posts: 16
|
 17 Jul 2009 22:36 transmission zero |
|
|
|
|
Hi all,
for analog filter, what does transmission zero mean? and what is difference between zero and transmission zero?
Thanks!
|
|
| Back to top |
|
 |
flatulent
Joined: 19 Jul 2002
Posts: 4877
Helped: 324
Location: Middle Earth
|
17 Jul 2009 22:48 Re: transmission zero |
|
|
|
|
| Unless stated otherwise, zero means transmission zero. With other modifiers it can mean impedance zero (short circuit to ground at a particular frequency).
|
|
| Back to top |
|
|
LvW
Joined: 07 May 2008
Posts: 1466
Helped: 242
Location: Germany
|
18 Jul 2009 10:03 Re: transmission zero |
|
|
|
|
| flatulent wrote: |
| Unless stated otherwise, zero means transmission zero. With other modifiers it can mean impedance zero (short circuit to ground at a particular frequency). |
Sorry, I donīt think so.
1.) "Transmission zero" means that there is a real zero with ideally zero volts at the output - for example like a notch or a low pass with Chebyshev/invers approximation.
2.) "Zero" means (in most cases, if not stated otherwise) that there is a complex zero - like in allpass cicuits. As a consequence the output of the filter goes NOT down to zero volts.
Added after 47 minutes:
Supplement for clarification:
By using the phrase "zero" always a zero of the transfer function is ment.
|
|
| Back to top |
|
|
Google
AdSense
|
18 Jul 2009 10:03 Ads |
|
|
|
|
|
|
| Back to top |
|
|
spree2007
Joined: 28 Oct 2008
Posts: 1
|
18 Jul 2009 17:03 Re: transmission zero |
|
|
|
|
as I know
Transmission zero is the zero placed in the "stopband" of filter
it can improve the selectivity at the expense of stopband attenuation
|
|
| Back to top |
|
|
edafisher
Joined: 25 Dec 2004
Posts: 16
|
19 Jul 2009 0:58 Re: transmission zero |
|
|
|
|
| LvW wrote: |
| flatulent wrote: |
| Unless stated otherwise, zero means transmission zero. With other modifiers it can mean impedance zero (short circuit to ground at a particular frequency). |
Sorry, I donīt think so.
1.) "Transmission zero" means that there is a real zero with ideally zero volts at the output - for example like a notch or a low pass with Chebyshev/invers approximation.
2.) "Zero" means (in most cases, if not stated otherwise) that there is a complex zero - like in allpass cicuits. As a consequence the output of the filter goes NOT down to zero volts.
Added after 47 minutes:
Supplement for clarification:
By using the phrase "zero" always a zero of the transfer function is ment. |
i agree with you more, to make it clearer:
in case 1 you mean the zeros in jw axis, thus we get infinite attenuation.
in case 2 you mean the zeros those are NOT in jw axis, we get finite attenuation.
this is because the zeros of H(s) are zeros of H(jw) only when they are in jw axis (s=jw).
so i think when talking about "transmission zero", usually it means case 1, namely the zeros in jw axis.
|
|
| Back to top |
|
|
LvW
Joined: 07 May 2008
Posts: 1466
Helped: 242
Location: Germany
|
19 Jul 2009 9:37 Re: transmission zero |
|
|
|
|
Hi edafisher,
thank you for clarification as I have expressed myself a bit misleading in my reply to flatulent.
When I say "real zero", of course I donīt mean a zero on the real axis but instead a "realistic" zero of the output voltage at a certain frequency. And this means as correctly stated by you: In the complex plane the zero is placed on the Im-axis.
Thak you, regards. LvW
|
|
| Back to top |
|
|
