Talk:Bode plot

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[edit] Straight lines

"It is especially useful in this case because the complex curves that appear in a linear magnitude-frequency plot can often be approximated by straight lines in a Bode plot."

Can't it always be approximated by straight lines? Isn't that how a Bode plot is drawn? It's just that the approximations are not so accurate for certain systems? Specifically, what are the straight line asymptotes for a Chebyshev filter? - Omegatron 16:36, May 17, 2005 (UTC)
I suppose the question is how accurately can it be approximated by straight lines (and how many straight lines you are going to use). RJFJR 16:43, 6 October 2005 (UTC)
Actually, I think it's more accurate (and correct) if the break frequencies are located at the radial distance from the pole/zero to the imaginary axis... —Preceding unsigned comment added by 99.235.205.120 (talk) 23:02, 18 February 2008 (UTC)

[edit] lowpass filter needs image

The comment about RC lowpass filter should ahve an image, but that is a particularly simple case so we probably want a more complicated one too. (Preference to bode-phase plot, I'd say). RJFJR 16:43, 6 October 2005 (UTC)

Image added. :-) — Omegatron 19:51, 8 October 2005 (UTC)

[edit] simples rules?

The article says: "These asymptotic approximations are useful because they can be drawn by hand following a few simple rules.",

but it doesn't say what they are. I think its talking about the rules:

For a transfer function in the form H(s) = A \prod \frac{(N_n)^{a_n}}{(D_n)^{b_n}}
where s = jω, N is a numerator term, D is a denominator term, and H is the transfer function.
  • start with a straight line at H(0)
  • at every value of s where N = 0 (a zero), increase the slope of the line by 20*an dB per decade.
  • at every value of s where D = 0 (a pole), decrease the slope of the line by 20*bn dB per decade.

For some reason s is equivalent to -ω when graphing. My explanation here isn't very well written, and probably has incorrect explanation. It would be very nice if someone could add this sort of thing onto the page. Fresheneesz 22:16, 4 May 2006 (UTC)

It's covered in the external links, too. I was going to add it to the article, but haven't gotten around to it. You know how it is... — Omegatron 23:12, 4 May 2006 (UTC)
Heh, yea, I'm only learning about them, so anything I might add is subject to stupidity. But maybe I'll hazard it anyway. Fresheneesz 01:57, 5 May 2006 (UTC)

[edit] complex poles and zeros

Needs something on complex poles and zeros - I'm not up for it. Fresheneesz 09:37, 14 May 2006 (UTC)

[edit] Merge

I have suggest that Bode plotter be Merged to Bode plot. 24.126.199.129 21:51, 22 August 2006 (UTC)

[edit] NonMinimum Phase?

whadaya think about adding stuff about TFs w/ -s+xn in the numerator or den. or other combinations of that sort? —The preceding unsigned comment was added by 128.46.105.66 (talk) 17:05, 8 December 2006 (UTC).

[edit] EngineersExcel.com

Recently EngineersExcel.com Excel Bode Plotter was added by User:Nitin Special:Contributions/Nitin.mehta and then removed by User:Dicklyon claiming is was an ad site, about a proprietary product. I've reviewed the site and I can't see anything wrong with it that breaks WP:EL. The Excel spreadsheets can be freely downloaded and used. As an engineer I would find tools like this useful. I propose keeping the link. --Rehnn83 16:58, 8 January 2007 (UTC)

It's OK with me if you decide it's worth keeping. My removal was based on the editor who was doing nothing but linking this site, so presumably a typical conflict-of-interest spam. The proprietary product I refer to is Excel. Dicklyon 18:26, 8 January 2007 (UTC)
ps. you can see from the site's main page that the editor is associated with it: [1]. So he should not be linking it; he should ask here and see if someone independent deems it worthwhile. Dicklyon 18:28, 8 January 2007 (UTC)
I can see your point, however I think Excel is a fairly common tool/programme and the worksheet would help with someones understanding of Bode Plots and therefore would benefit the article. For now I'm going to leave the article as it is for now pending further discussion. - Rehnn83 20:27, 8 January 2007 (UTC)

[edit] "Unstable" poles and zeros

If a pole (or zero) is negative, its phase contribution should be the opposite, right? Anyone can confirm this? (by the way) we really need to write something about complex poles or zeros) --Arcturus4669 21:56, 5 June 2007 (UTC)

No, poles and zeros are not signed. Dicklyon 22:04, 5 June 2007 (UTC)
Sorry, I used the wrong word. I mean "unstable" poles and zeros (that is, having a positive real part leading to a diverging exponential contribute), such as the zero in
G(t) = \frac{s-3}{s+1}
--Arcturus4669 15:18, 6 June 2007 (UTC)
Oh, right, you mean right-half-plane poles and zeros (the zeros aren't unstable, but the poles are). Yes, they make the phase go the other way. Dicklyon 17:52, 6 June 2007 (UTC)
Ok, I added the information. Feel free to change wording to whatever is the usual way to refer to positive-real-part singularities in English (in Italy we generally refer to them as "unstable" zeros and "non minimum phase" systems) --Arcturus4669 13:28, 10 June 2007 (UTC)

[edit] Application

The article is unclear about what are the purposes and applications of Bode plots. Can somebody just add a line about this? Riki 08:34, 18 August 2007 (UTC)