How to get envelope from AM signal without phase shift
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From: WWalker on 29 Mar 2010 17:25 Rune, Now you are being rediculus! The dipole solution has been derived hundreds of times in hundreds of ways over the last 100 years. They all agree with the transfer function I used in my simulation, and agree that the solution is valid in the nearfield provided the distance to the analysis point is much less than the length of the dipole. It has also been derived using spherical harmonics resulting in the same result (Ref. Electrodynamics, James Blake Westgard, 1997). I have also derived the solution from Maxwell's Equations in my paper, and I have also measured the dispersion of a real magnetic dipole antenna with a RF Network Analyser and I get the same nonlinear nearfield phase vs frequency curve. So the effect is clearly real. William >On 29 Mar, 17:06, "WWalker" <william.walker(a)n_o_s_p_a_m.imtek.de> >wrote: >> Rune, >> >> The transfer function I use in my simulations is well known for the >> magnetic field component of an electric dipole: (1/r^2)e^(ikr)[ikr-1]. You >> can look this up in any EM book or look at my paper Eq. 46 were I have >> derived it from Maxwell Equations, > >Neither the textbooks nor you have derived anything. >You (and the textbooks) refer to tabulated approimation >you don't understand how were derived, or the extent >of their validity. > >The key to pinning down the causes of your incompetence >is to derive the results from scratch. I have already >told you how to do this in a different post. > >> It is well known and stated clearly in most text books that the model is >> only valid provided the distance to the observation point is much larger >> than the dipole length. > >Again: Your problem is that you don't understand the basics. >Start with the monople. The results you have "derived" are >only valid in the far field of the monoploe (which, of course, >you would have known had you *read* my previous posts). Once >you understand it fully, you might advance to the dipole. > >As I said before: Your ego is your problem. There is no point >refering or listiong results if you don't contemplate their >impact and consequences. You have demonstrated a unique >ability *not* to think. > >You will not get anywhere unless you acknowledge that fact. > >Rune >
From: glen herrmannsfeldt on 29 Mar 2010 17:30 Eric Jacobsen <eric.jacobsen(a)ieee.org> wrote: (big snip) > How did the input "pulse" get bandlimited in the first place? This is > key to understanding how this works. It's not magic, information is not > accelerated. > Imagine this and you might be able to see what's going on: > Start with an ideal impulse, a dirac delta, or some suitable equivalent. > Pass that impulse through your bandlimiting filter, see how long it > takes to come out. Since the bandlimiting filter is causal, the bottom > of the leading edge of the pulse doesn't happen until the instantaneous > impulse has arrived. The entire width of the output pulse is then a > delay from the incidence of the impulse. > Consider the dirac delta the "information". Well, that doesn't seem quite fair. If you take the output of the filter, and then pass it through the transmit/receive system, and then determine the delay, that seems a better test. But... > So, it is easy to see that the peak of the output pulse has, at minimum, > the delay from the bottom of the leading edge of the bandlimited output > pulse. > If you closely examine the output of the predictive filters, whether > it's a filter with a negative group delay or the near field of an > antenna or whatever, it does NOT begin to ramp up the output pulse > values until the input pulse values have actually arrived. In other > words, as we know, or at least most of us know, such a filter is still > causal and does NOT predict the onset of the leading edge of the pulse. There are reference in the Wikipedia page to an experiment by Boyd that seems to show faster than light behavior for, not surprisingly, light! (It also does not claim to violate special relativity.) The experiment uses erbium doped optical fibers. As well as I understand it, the fiber amplifies the incoming signal and, slightly later, generates a signal to cancel the rest of the incoming signal. My best thought in terms of analog electronics is to consider a very high gain amplifier with an insufficient power supply. Say, for example, with filter capacitors that charge through a large resistor. Now, when the leading edge of the pulse comes in it will be amplified by a large factor, resulting in a new pulse. By the time the peak arrives, the filter capacitors have discharged, and the output no longer follows the input. I believe that isn't so far from what is done with erbium doped fiber. The erbium atoms are put into a higher energy state, and then the signal comes in. A Gaussian envelope wave train has a nice, oscillatory, leading edge ready to cause the erbium to emit well before the peak. To me, a better test is to do a correlation between the input and output for an appropriately band limited noise source. (Maybe white noise through an appropriate filter.) The peak in the correlation integral indicates the delay, on average, through the system. Measuring the delay of a single transition, or peak, can too easily give the wrong value. -- glen
From: WWalker on 29 Mar 2010 17:36 r b-j, But, the research presented in this thread indicates that the EM signal speed in vaccuum is faster than light in the nearfield and only reduces to the speed of light in the farfield. If this is true, then in your opinion, how would this affect physics? As you said, a lot of physics is based on the speed of light being constant, but what if it is not? William >On Mar 28, 4:13=A0pm, Eric Jacobsen <eric.jacob...(a)ieee.org> wrote: >> On 3/28/2010 11:40 AM, WWalker wrote: >> >> > I am sorry to insist, but it does not matter what the reason is. =A0If = >I have >> > a communication link that allows me to transmit a pulse over a distance >> > faster than a light propagated pulse, then the pulse propagates faster = >than >> > light. >> >> I suppose you can argue semantics here about what defines the "pulse", >> but understand that "information" is not propagating faster than light >> in any of the examples, and neither is energy. =A0This seems to be the ke= >y >> point that must be understood. =A0 A simple small phase advance of a >> signal is NOT indicative of information exceeding the speed of light. >> >> If you just want to claim that the signal has phase advanced and appears >> to arrive earlier than expected, that's fine, I don't think anyone will >> argue with you there. =A0That's what has led to discussion and study on >> this topic in many places. >> >> > If I use the pulse to denonate a bomb located a distance away, the >> > bomb will explode sooner than if the pulse propagated at the speed of >> > light. This is absolutely true and cannot be argued. > >well, it *is* argued. > >this is funny, because i have been in similar discussions but on >sci.physics.research or sci.physics.foundations or, in the past, the >Physics Forums site. i haven't seen it here on comp.dsp. sometimes >the discussion is about the speed of gravity (in comparison to the >speed of electromagnetic propagation a.k.a. "speed of light"). now, i >*do* seem to remember reading something about the group velocity of >some modulated light source exceeding the phase velocity in some >medium. i don't usually concern myself with non-vacuum propagation >since, at the atomic level, it's a vacuum between the atoms and when >epsilon differs from epsilon_0 it's a macroscopic *aggregate* effect >of the polarization of molecules in the medium. same with mu and >mu_0. > >the speed of light (or of EM) in a vacuum, what we call "c", is not a >property of E&M, but is a property of space and time. it doesn't >matter what the "instantaneous" force or interaction is. could be EM, >gravity, strong (turns out weak is mediated by particles with mass, so >it ain't as instantaneous). > >suppose you are standing there and i am standing here, some distance >away. now suppose you are holding a big negative charge and i am >holding a big positive charge and we are both restricting the movement >of our charges to a plane that is perpendicular to the line connecting >the two of us. since our charges are attracted to each other, when i >move my charge up, your charge follows it up. if i move it down, your >charge follows it down. if i move it to my right, your charge follows >it to your left (assuming we are facing each other). similarly if i >move my charge to my left, your charge follows to your right. if i >move my charge up and down repeatedly, yours will follow it up and >down repeatedly. i am literally a "transmitting antenna" and you are >a "receiving antenna". if i move my charge up and down a million >times per second, you could tune it in with an AM radio. if i move it >left and right 100 million times per second, you can tune it in with >an FM radio. if i move it back and forth 500 trillion times per >second, you would see it as a blur of orange color. that's what EM >radiation is, at a fundamental level. > >now imagine there is a third party observing us at a distance and is >equidistant from us both. and suppose this third party knows, from >some other means, what the distance is between us. no matter what i do >with the charge, when the observer sees the perturbation of position >on my end and then observes a perturbation at your end, the time >differential between the cause and effect will always be that distance >between us divided by c. i don't care what you read or what you think >W, that's what it is. > >it would be the same if you and i were the size of gods and, instead >of charges, i was holding a planet and you were holding a planet. i >perturb the position of my planet and your planet will get disturbed >by that change of gravitational field and the time differential >between the disturber and disturbed will be the distance between the >two of us divided by the *same* c. so, even if we tried to use >gravity waves to communicate information, we would still be limited by >the speed c. > >now, despite what we sometimes read, it isn't that Nature is imposing >a fundamental limit to the speed of propagation of information, it's >that Nature, namely the fundamental nature of space and time, imposes >a finite limit of speed of the fundamental interactions, of which all >of physical reality is built upon. *that* is what imposes a limit of >speed of conveyance of information since information is conveyed by a >physical interaction. > >there is nothing magical about that speed "c". all the physics needs >is that c is real, positive, and finite. it could be *any* speed (as >observed by a god-like observer who is not himself affected by the >physics). for those of us who are mortal and are governed by the >interactions of Nature, all of the rest of reality would be scaled in >such a way that the speed of propagation, c, would appear to be the >same, *unless* some *dimensionless* fundamental physical constant >(like alpha) changes. and then, the salient fact is that this >dimensionless "constant" changed (not c). we don't measure or >perceive dimensionful quantities directly, but we *always* measure or >perceive such as a ratio against a reference quantity of the same >dimension. there is always a reference voltage in our DVM, there are >always pre-existing tick marks on our ruler. the dimensionful >quantity we call "c" is more of an expression of the anthropometric >units we happen to be using to measure length and time. > >WWalker, i might suggest that you take this up at >sci.physic.foundations or maybe sci.physics.research (both are >moderated) or go to the PhysicsForums.com site. > >r b-j >
From: WWalker on 29 Mar 2010 17:53 Jerry, Dopler radar is used to measure object velocity and if this is done in a particle accelerator experiments, the results could be missleading if not interpreted correctly. In addition, my analysis has shown that fields generated by a dipole source never achieve a constant velocity, they just approach it in the farfield. So doppler measurements in the farfield will differ also by a small amount. As farfield dopler radar becomes more sensitive it will eventially have to deal with the effects I am discussing. William >WWalker wrote: >> Jerry, >> >> The speed of light is a corner stone in physics and if it is not a constant >> then many of our theories in physics will be affected. There may be direct >> practical uses as well, but I just guessing: improving accuracy of high >> speed doppler radar, speeding up communication to spacecraft where time >> delays are problematic, increasing speed of computers when they are >> eventually limited by light speed delays etc. As I said, these are only >> guesses, the main effect would be a change in many of our theories in >> physics, which would eventually lead to new practical uses and >> technologies. >> >> William > >How much Doppler radar is done within half a wavelength of the antenna? >One might as well use a tape measure for distance, and if the Doppler >shift amounts to anything, duck! > > >Jerry >-- >Discovery consists of seeing what everybody has seen, and thinking what >nobody has thought. .. Albert Szent-Gyorgi >
From: WWalker on 29 Mar 2010 18:15
Eric, The first pulse is not the signal fed to the dipole. The first pulse is just used to create a narrow banded pulse, which is then sent through the dipole to be detected. Forget about the first pulse, the question is if I send a narrow banded pulse through the dipole how long will it take to arrive across a region of space in the nearfield of the dipole. If the answer is less than the speed of light to cross the same region of space, then the pulse has propagated faster than light. "So if press a button with the same signal characteristics as the LPF pulse, and if I use the threshold detector set jsut above the noise level to detect the pulse and explode a bomb, the bomb will explode earlier than if the pulse propagated at the speed of light. The pressing of the button (Action) results in the exploding of a bomb (Reaction) faster than light speed. This is clear cause and effect (information) which propagtes faster than light." William >On 3/29/2010 8:42 AM, WWalker wrote: >> Eric, >> >> Could you elaboate on your comment below. I think we need to agree on the >> definition of information in regards to the LPF pulsed carrier simulation. >> How does your comment refute my argument presented again below? >> >>> I suppose you can argue semantics here about what defines the "pulse", >> >> Again I claim: >> >> "Refering to the Low Pass Filtered Pulse >> simulation I posted, the simulation clearly shows that if I transmit a >> pulse, the pulse edge arrives sooner than if it had propagated faster than >> light. If my detector at the receiving end is a threshold detector which >> is >> set to look for anything above the noise level, it will fire earlier than >> if the pulse had propagated at light speed. In other words, it shows that >> if I push a button launching the narrowband pulse signal and propagate it >> via a dipole to a nearfield receiver with the threshold detector, the >> pressed button will be detected sooner than a light propagated signal. >> This >> clearly shows that an action (informaton) in this nearfield dipole system >> can be detected faster than light. If this is true than I have proven my >> point that information propagtes faster than light in the nearfield of a >> dipole." >> >> "it does not matter what the reason is. If I have >> a communication link that allows me to transmit a pulse over a distance >> faster than a light propagated pulse, then the pulse propagates faster >> than >> light. If I use the pulse to denonate a bomb located a distance away, the >> bomb will explode sooner than if the pulse propagated at the speed of >> light. This is absolutly true and cannot be argued. The only question is >> if >> the dipole simulation demonstrates that a pulse can be detected over a >> distance faster than light. I think it has. >> " >> >> So if press a button with the same signal characteristics as the LPF pulse, >> and if I use the above setup to detect the pulse and explode a bomb, the >> bomb will explode earlier than if the pulse propagated at the speed of >> light. The pressing of the button (Action) results in the exploding of a >> bomb (Reaction) faster than light speed. This is clear cause and effect >> (information) which propagtes faster than light. >> >> >> William > >How did the input "pulse" get bandlimited in the first place? This is >key to understanding how this works. It's not magic, information is not >accelerated. > >Imagine this and you might be able to see what's going on: > >Start with an ideal impulse, a dirac delta, or some suitable equivalent. > Pass that impulse through your bandlimiting filter, see how long it >takes to come out. Since the bandlimiting filter is causal, the bottom >of the leading edge of the pulse doesn't happen until the instantaneous >impulse has arrived. The entire width of the output pulse is then a >delay from the incidence of the impulse. > >Consider the dirac delta the "information". > >So, it is easy to see that the peak of the output pulse has, at minimum, >the delay from the bottom of the leading edge of the bandlimited output >pulse. > >If you closely examine the output of the predictive filters, whether >it's a filter with a negative group delay or the near field of an >antenna or whatever, it does NOT begin to ramp up the output pulse >values until the input pulse values have actually arrived. In other >words, as we know, or at least most of us know, such a filter is still >causal and does NOT predict the onset of the leading edge of the pulse. > >So, what you are seeing is, for example, because I don't know the actual >numbers from the simulations, the distance from the initial dirac delta >to the bandlimited output pulse peak being X, and the "accelerated", >predicted pulse output is X-delta, where delta is the small advance >achieved by the prediction. NOTE THAT X-delta IS STILL A POSITIVE >NUMBER, and delta is going to be small compared to X. > >All filters have delay. What you are seeing is that the predictive >filter has a little less delay than the signal being compared to it. >The "information" arrival, as compared to the actual incidence of the >initial dirac delta, will not violate causality or c. Observers can be >fooled, however, as you are demonstrating. > > >-- >Eric Jacobsen >Minister of Algorithms >Abineau Communications >http://www.abineau.com > |