Hi,
I have the books by Archambeault, Ott, Morrison, Young and countless application notes. I can recite Maxwell’s equations by heart and I know of the Telegraphers equations. However, I would like, if someone can point me to it, a reference to a paper or book that shows the mathematics behind what people talk about when they say “the signal is in the field not in the conductor”. I have researched the Poynting vector and what that means and believe it or not there is still discussion about that.
I do hear a lot of “verbiage” saying “do this and do that” and there are app notes and “rules” for making PCBs that work that have been around for years now. But, I would like to be able to explain the “field theory” that I am referring to without a lot of “hand waving”.
I believe the “hand waving” I just want to be able to prove it.
Thank You
Tom
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I recommend that you research Ralph Morrison. His work is now being presented by Dan Beeker. I attended one of Dan’s very worthwhile 2 day webinars (Billion Dollar Mistake - hosted by Sierra) which likely will help you in your quest.
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I would suggest you start with my article, The Billion Dollar Mistake, to begin your journey into EM field behavior. The Billion Dollar Mistake
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Daniel,
thank you for your reply. Yes, I did read your article, “The Billion Dollar Mistake” before I made the original post. FYI, like yourself, I am experienced (I’m an “old guy”). I have fixed many EMI problems over the years and I won’t get into that (some of the stories would, I am sure, “curl” your hair). But as I own and am reading a book by Ralph Morrison, the following “struck me: On page 53 of “Fast Circuit Boards” by Ralph Morrison, it says “The energy behind the wave front is carried at the speed of light in both the E and H fields although the fields are unchanging”. As it is shown in your article about the Billion Dollar mistake, the wave front is moving, even though the fields behind the wave front are not changing.
The “mystery” as I see it, is, what is causing the wave front to move after it is initialized, shall we say? Is it some sort of conservation of fields issue? Ok, you start out with a switch and as the switch starts to close, the fields within the space or dielectric, begin to change and then stabilize. Simply put, If the fields stabilize then what causes the wave front to keep moving? And, is there a way to mathematically state this (again, is it some property of conservation of the fields?).
Thank You
Tom Cipollone
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That is where the real magic is. Ralph said there was something we were missing at the quantum level and he was studying that before he passed away. The motivation at a simple level is the need to reach equilibrium. Once the spaces are connected by the two conductors, the higher charge density in one space will try to fill the new space. Once the field density is uniform, the changes stop, and if the impedance is matched, the energy moves, primally carried by the H field, like a driveshaft in a car, per Ralph’s explanation. My simple perspective.
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Thank you for your reply but most of all, thank you for your honesty, a rare commodity these days.
I spend the weekend doing research and I am no physicist. I am an E.E. and a board designer, like you. I had thought a lot about the Poynting theorem possibly satisfying the energy transfer. Here is a video that has stirred up a lot of controversy but seems to go along with what we as PCB designers are thinking, in terms of the energy traveling in the field and not the wires.
However, there are a number of people that disagree with this. One of the leading critics of Poynting is “Kathy loves Physics” as shown in some of her videos.
However, in the comments in her lectures (this one and other ones). there is disagreement about her disagreement, in that she claims that Richard Feynman, the famous physicist, had said that the Poynting theorem was “crazy” whereas there are other physicists that say that he was only being sarcastic. My only “beef” with the famous is that there seems to be inconsistency with the direction of the Poynting vector. Feynman seems to have rewritten it in order to make more sense.
So, this last video, done fairly recently, seems to put the Poynting vector in a perspective which is more aligned with what was we as non physicists but practitioners of the art of PCB design seem to believe. I can not put the link to the video due to restrictions but the video is called “Energy flow in EM waves” by David Bowler.
I would appreciate your feedback.
Thank You and Best Regards
Tom Cipollone
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There is a chance that you’re overthinking it. A very over-simplified model is that electricity is like water inside a pipe, and the energy flows by stuff (electrons rather than water molecules) physically moving. (They even do move, though not nearly as fast as the signals.) Saying that the energy/signal is in the field is a way to push back against this, and a reminder that you have to consider the dielectric and the geometry, instead of just the copper connectivity.
I’m not saying it doesn’t also have the deeper meaning that you’re looking for; I am saying that it might be said almost as often even if there were no deeper truth to unravel. So even the final “there” there might be less satisfying than you hope.
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Jim,
Thank you for the reply. Of course, it is always possible that I am “overthinking” the situation, as you say. 
. I am not a physicist, as I have said, and I don’t get paid to impersonate one. But, it seems that the more I read, the concept of energy moving in the field, is not at all strange to physicists. There is a lot of discussion about the Poynting theorem, and I am quite willing to leave it there. I’ve been reading Ralph Morrison’s book “Fast Circuit Boards” page by page and there is only a short section where Poynting is discussed. For example, in the preface (not even the introduction) he writes “I had some questions about Poynting’s vector and step functions and got no help from my physics friends”. And then, in section 1.20 “Poynting’s Vector” he sates “ A transmission line carries energy from a decoupling capacitor to a logic gate in the space between a trace and a ground plane. Space carries energy. Conductors direct where the energy travels”. But, in section 2.8 “The propagation of a wave on a transmission line” he writes about “initial wave action” but in that section does not mention the Poynting vector at all.
Here is my two cents for what it is worth. Not that I would be able to engage in a debate with the venerable Ralph Morrison, were he still alive ( I am sure he would have smacked me up the side of the head). My guess is that Mr. Morrison simply did not believe in the Poynting vector and its role in “wave action”. Energy transmission, yes, but wave action…I think that he was still looking for some action at a distance mechanism that he never found. I don’t believe that he thought that energy transmission and wave action were one in the same thing. But then, as you say, I could be overthinking it.
Best Regards
Tom Cipollone
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