Talk:Phase (waves)

message: The confusion below speaks to the need to re-write the article in toto, IMO. -Dawn McGatney  —Preceding unsigned comment added by McGatney (talk • contribs) 10:06, 21 January 2008 (UTC)
thread_title: Confusion

message: Do physicists really use φ(x) for the wave function and φ0 for the phase?  — Omegatron 22:37, 31 October 2005 (UTC)
replies: text: Looks right to me. Smtomak 01:16, 28 June 2007 (UTC)
thread_title: Physicists

message: The test refers to entities called A, B and C.  Are these waves?  Are they the waves in the diagrams?   Some clarification would be nice for people who do not know this material.
:I think they refer to older diagrams that were replaced without updating the text. — Omegatron 20:00, 28 November 2005 (UTC)
thread_title: Text references

message: I removed the following, which refers to a diagram that no longer exists:
--Heron 18:21, 18 June 2006 (UTC)
replies: text: Why does the diagram no longer exist? — Omegatron 00:56, 19 June 2006 (UTC)
replies: text: Because its been deleted? 8-)--Light current 01:11, 19 June 2006 (UTC)
replies: text:  Is it worth reproducing, though? — Omegatron 19:02, 23 June 2006 (UTC)

text: I dont know. I have not seen it 8-|--Light current 19:15, 23 June 2006 (UTC)
thread_title:  Removed obsolete material 

message: *Agree with all proposed merges. 8-)--Light current 19:45, 23 June 2006 (UTC)
thread_title:  Merging- 

message: Jimmy Wales has said of this: "I can NOT emphasize this enough. There seems to be a terrible bias among some editors that some sort of random speculative 'I heard it somewhere' pseudo information is to be tagged with a 'needs a cite' tag. Wrong. It should be removed, aggressively, unless it can be sourced. This is true of all information, but it is particularly true of negative information about living persons." [1][2]
If its not policy, why is it on the policy page?--Light current 00:46, 24 June 2006 (UTC)
replies: text: And this has what to do with the image? — Omegatron 03:51, 24 June 2006 (UTC)
replies: text:  Nothing.  The image is not incorrect.  It is not pseudo information.  It does not require a source.  Could it be even better?... yes.  Is it better than nothing?... yes.  Is this debate a waste of time?... yes.  --Bob K 05:01, 24 June 2006 (UTC)

text: No.  I am expressing a different 'O'pinion than yours.  I was not misled by the image, but I did have to stop and think about it.  Also note that the image does not stand alone in a vacuum.  There is explanatory text, notably this:    "Thus, a shift in time is equivalent to a change in the initial phase.  Conversely, a change in the initial phase is tantamount to a shift in time."  --Bob K 13:08, 24 June 2006 (UTC)

text: Which is what the whole article is about.  I guess you just need to have the last word, so go ahead.  Unless it contains some actual substance, I will leave it alone next time.  --Bob K 22:33, 24 June 2006 (UTC)

text: Very nice.  I suggest we add a link to that site.  --Bob K 00:16, 25 June 2006 (UTC)

text: Doh!  You are absolutely right, but I had to check google to find out.  It is apparently a bad habit of mine that I have been doing for so long that it looks perfectly normal to me.  And this is actually the first time anyone has asked about it.  Feel free to fix them, if so inclined.  I will try to do better in the future.  --Bob K 07:21, 27 June 2006 (UTC)
thread_title:  Extract from WP:V 

message: Just moving the template here where it belongs. -- Your friendly, neighborhood housekeeper, Flex 14:41, 6 September 2006 (UTC)
replies: text: The first sentence of this article could really bear clarification - maybe even breaking into different sentences.  "fraction of a complete cycle corresponding to an offset in the displacement from a specified reference point.." - what?? offset, displacement, and  reference point are all so closely conceptually related I wonder if they aren't the same thing explained three different ways.. andf how does this fraction correspond to all that whatever? --166.70.188.26 (talk) 16:49, 30 June 2008 (UTC)

text: Moreover the diagram does apparently nothing (for a novice's eyes anyway) to show where the phase is identified in the waveform.  Shouldn't it say "phase" somewhere?  And is "period" in the diagram another way of saying "cycle" (in the sentence)? --166.70.188.26 (talk) 16:52, 30 June 2008 (UTC)
thread_title: Technicalia

message: It is important to mention that the phase is zero when the wave is maximal.
It is mentioned in the definition of "Instantaneous phase", but it should be mentioned here too.
:Please sign your comments.  First of all, sin(0) = 0, and max( sin ) = 1.  Secondly, t=0 is kind of a "starting point", and it seems more intuitive (to me) for a wave to start at level 0 and rise to its apex, like a mountain, rather than for the apex to just "appear" out of nowhere.  So I prefer to keep the sin() function.  Third, why would it be "important" to mention any of this?  It seems rather minor.
:--Bob K 15:15, 27 June 2007 (UTC)
thread_title:  Phase=0 

message: Yes please MarkAnthonyBoyle 08:48, 27 September 2007 (UTC)
thread_title: Merge with Antiphase

message: "Instantaneous phase has a formal definition that is applicable to more general functions and unambiguously defines a function's initial phase at t=0." This is definitely wrong, compare with the article about instantaneous phase.
Pk72 (talk) 08:54, 7 July 2011 (UTC)
thread_title:  Instantaneous phase 

message: A recent mass change replaced all the θ's with φ's, with the explanation: "Try to impose a little bit of consistency in notation. Most of the time, the convention is θ for the entire angle or argument to the sin() function and it's φ for the phase offset."  I'm all for consistency, but is that statement a correct one?  In my experience, instantaneous phase is always written as φ(t), and the instantaneous phase of  \scriptstyle \cos( 2 \pi f t + x)  is  \scriptstyle \phi(t) = 2 \pi f t + x.   So θ is a better choice (than φ) for x.   --Bob K (talk) 14:13, 16 February 2012 (UTC)
replies: text: Lower case phi – φ – is the correct symbol for phase in terms of practical electronics. As a live sound engineer, I might point out that the Danish letter Ø has often been used to label a switch in polarity. I bring that up because a flip in polarity is often considered by sound guys to be the same as 180° of phase shift at all frequencies. Binksternet (talk) 19:33, 16 February 2012 (UTC)
thread_title:  θ or φ? 

message: I am wondering if it may be worth to make a difference of the phase term discussed here with the phase term in the complex domain representation of signals. For example, a sinusoidal signal (real) can be represented in magnitude-phase, and its phase (which in this case can be understood as the angle with respect to the positive real axis) takes only 0 or pi radians. We even can add a "phase shift" to the aforementioned signal but the signal phase will still take 0 or pi radians. For example, cos(wt) and cos(wt + phi) can be thought of a real vector in the complex domain varying its magnitude from 1 to -1 periodically. What do you think?  — Preceding unsigned comment added by EthanZur (talk • contribs) 11:42, 3 May 2012 (UTC)
thread_title:  Phase term in "magnitude-phase" representation of signals

message: The explanation is vague and it isn't tied in with the figure.  What part of this circuit represents phase compensation and what part represents the phase to be compensated?  What amplifier stage is switched into the signal path?  Is the amplifier in the figure part of a larger system? Constant314 (talk) 00:54, 4 September 2012 (UTC)
replies: text: Upon further reflection, phase is a subject that transends electronics.  I'm not sure that an electronic circuit should even be part of this subject.Constant314 (talk) 13:55, 6 September 2012 (UTC)
thread_title:  Clarification requested on the Phase Compensation section 

message: The figure purports to illustrate a phase compensation circuit.  But, the circuit has no dc feedback and could not work as a standalone circuit, although it could be an element of a larger system where there was overall dc feedback.  But even then it’s not likely to produce useful phase compensation.  At low frequency this circuit is an integrator with produces -90° degrees of phase shift.  As frequency increases (assuming C1 >> C2) the circuit starts to resemble straight gain for frequency greater than ω₁ = 1/ (C1 x R2) and less than ω₂ = 1/ (C2 x R2).  Above ω₂ it again resembles an integrator with phase shift of -90°.  So, looking at the phase shift of this circuit, it starts out at -90°, then it increases toward 0°, but stays slightly negative and then decreases toward -90°.  This circuit adds negative phase at most frequencies which is usually the opposite of what is needed to stabilize a loop.  A lead-lag configuration would be a typical example of phase compensation of a larger loop. Constant314 (talk) 13:44, 6 September 2012 (UTC)
thread_title:  Phase compensation, figure is dubious 

message: The article is about phase which is a very general concept.  Phase compensation is a technique used to change the phase shift of an electrical circuit or other linear system.  Phase compensation is often used to stabilize circuits and systems that use feedback.  A factually correct section about phase compensation might logically appear in an article about feedback, opamps or servos among others.  It is out of place in this article.
The figure has no explanation of how the circuit works, what it does or how to use it.  The particular circuit depicted is unlikely to be used for phase compensation because its phase shift is always negative.
Phase compensation is not a correction for phase error.  It can be used to adjust the phase shift of a circuit.
Phase compensation is not required to obtain stability in an opamp but it can be used to improve the phase margin of an opamp and it can be used to stabilize a circuit that includes an opamp.
Phase compensation does not subtract out an amount of phase shift from a signal which is equal to the amount of phase shift added by switching one or more additional amplifier stages into the amplification signal path. Constant314 (talk) 22:37, 23 December 2012 (UTC)
thread_title:  Removing Phase Compensation 

message: I came here looking for the promised discussion about a merge with Instantaneous Phase.  Nobody home.  Well anyhow, I vote "no", because this article is about a constant, and the other article is about a time-variant function.
--Bob K (talk) 17:57, 18 October 2013 (UTC)
thread_title:  Merge with Instantaneous Phase 

message: I vote no, since phase angle can be applied to any complex number or 2D vector, while the phase of this article is only applicable to waves. Ulflund (talk) 11:50, 12 January 2014 (UTC)
thread_title:  Merge with phase angle 

message: The following statement is incorrect, unnecessarily complicated, and not particularly relevant:
An equivalent formula is (see List of trigonometric identities#Linear combinations):
:x(t) = A_s\cdot \sin( 2 \pi f t ) + A_c\cdot \cos( 2 \pi f t )
where \varphi = atan2(A_c,A_s) and A = \sqrt{A_s^2+A_c^2}.
The incorrect part (fixed) is:  \varphi = atan2(A_c,-A_s)
A simpler statement, but still not helpful would be:
:x(t) = A\cos(\varphi)\cdot \cos( 2 \pi f t ) - A\sin(\varphi)\cdot \sin( 2 \pi f t )
--Bob K (talk) 13:52, 24 November 2014 (UTC)
replies: text: I'd call the missing minus sign a typo, not a completely incorrect expression. Could you please to elaborate why you find it unhelpful? I find the expression helpful in practice because it shows how to extract phases out of FFT coefficients, for example. It also illustrates the more theoretical point that Cartesian and polar complex representations are equivalent. Thanks. Fgnievinski (talk) 18:46, 24 November 2014 (UTC)

text: (after ec) Actually, I think that that expression gives the co-angle of φ because φ is defined in the article as the phase shift from the cosine, not the sine.  I think the point being made is that a phase shifted sinusoid is always the sum of a sine and a cosine wave (and vice versa).  That is a worthwhile point to make, with or without formulae. You need to know this in Fourier analysis for instance, and if you are the designer of a spectrum analyzer. SpinningSpark 18:56, 24 November 2014 (UTC)
thread_title: Linear combination

message: This article only seems to discuss phase as a function of one variable, such as time, even though there are various examples of ones that rely on two or more variables. For example, the phase of a plane wave might take the form \phi = k z - \omega t, which is consistent with its usage in the Jones calculus article.
So unless I'm missing something, this article might need a rewrite, because it currently only defines phase for the one variable case. Thoughts?
Badooga (talk) 05:07, 17 March 2021 (UTC)
thread_title:  Multivariate Phase