How to get envelope from AM signal without phase shift
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From: Eric Jacobsen on 25 Mar 2010 12:54 On 3/25/2010 8:45 AM, WWalker wrote: > Eric, > > A narrow band AM signal propagates undistorted and faster than light in the > nearfield and reduces to the speed of light as it goes into the farfield. A > pulse distorts in the nearfield and and realigns as it goes into the > farfield. When the pulse is distorted, one cannot say anything about the > speed of the pulse. To transmit information faster than light one must use > narrowband signals like AM and transmitt and receive them in the nearfield > of the carrier. > > It is true that a real dipole anntena has filter characteristics. The > simulation I presented is an idealized dipole like an oscillating electron > which does not have filter characteristics. In an experiment with real > antennas one would have to subtract out the phase shifts due to the > antennas filter characteristics so that one only sees the time delay > behavior of the propagating fields. > > The signals I used in my simulation are a changing modulation over the time > window of analysis. The changing modulation does not repeat over this > window. It is true that they are created from deterministic signals. > Bassically I generated a beat frequency modulation which has a carrier and > a modulation frequency. Provided the window of analysis is smaller than a > modulation time period, the modulation pattern does not repeat. After a > modulation period the patern repeats again. I chose this type of signal > because it is a changing pattern which eventually repeats, enabling me to > trigger it in a real experient and also enabling me to do time averaging > which will help a lot with improving the SNR if a experimental signal. The period of the signal isn't necessarily consequential, the fact that it is not random is. The point being that the signal you are using is not suitable for measuring propagation at the resolution you're interested in because it is a deterministic signal. Even when there's a component that is randomly changing with time it is easy to get fooled by the nature of narrowband signals, and that was pretty much a big point of Andor's paper. I'm beginning to see why he chose the title that he did. > When perform an autocorrelation of the modulation I used in my simulation, > I see a triangular signal with a peak at the time of the analysis time > window, indicating that the signal has no obserable repetition pattern of > the this time. Only after I increase the analysis time window greater than > the modulation period do I get significant sidelobes in the autocorrelation > signal, indicating that the pattern repeats after each multiple of a > modulation cycle. Again, how many periods you observe isn't what matters when the signal is completely deterministic. You're just observing the same, informationally-static signal over different periods of time. That tells you little to nothing about the propagation of information. > Of course I can create a random narrowband signal as was done in the OpAmp > resonator paper: http://www.dsprelated.com/showarticle/54.php > modulate it with a carrier and pass it through a dipole system, and finally > extract the modulation, and compare it to a light propagated signal. If > this is done you get exactly the same answer as I showed in my simulation. > But if this technique is used than I can not use time averagiing to improve > SNR which is need for detection of the modulation in real experimental > signals. I have perfomed this random modulation simulation using Agilent > Vee Pro software which is not possible to show here in text format. But I > can try to describe it. I took a 100V random generator and sent the signal > through a 50 MHz cutoff (fc), 6th order LPF with the following transfer > function [1/(j(f/fc)+1)^6]. Then I multiplied it with a 500MHz carrier and > sent it though a light speed propagating transfer function [e^(ikr)] and > though the magnetic component of a electric dipole transfer function > [e^(ikr)*(-kr-i)]. Finally I extracted the modulation envelopes of the > tranmitted signal, light speed signal, and the dipole signal. To extract > the envelopes I used squared the signal and then passed it through a 300MHz > cutoff (fc), 12th order LPF with the following transfer function > [1/(j(f/fc)+1)^12]. Again, be careful even when there is a random component, as the narrow band predictability of the signal can easily appear to be accelerated propagation, as Andor demonstrated. He hit it spot-on, IMHO, by showing a pulse appear to arrive before the stimulus, but then demonstrated that interrupting the source proved that the signal was, in fact, causal after all. A train of such pulses can be modulated with a random component, but if one isn't extremely careful I'd think it'd be pretty easy to make an incorrect conclusion about what was propagation and what was just typical band-limited predictability. This is why I suggested interrupting your transmit signal at some point, perhaps even at a zero crossing, because it may help to see what's really going on. Your burden of proof is large, and it appears to me that you're not at all very far down the road of sufficiency if you're not addressing these issues head on. Your continued use of a completely deterministic signal for propagation measurements suggests to me that you've not been measuring what you think you have been. I think you want a signal with enough entropy to justify your claims. The signals you're using are nearly entropy-free. I suspect there's a relationship between signal entropy and the sort of resolution or confidence you can have in a propagation measurement, but I don't know what it might be off the top of my head. If you had such a demonstrated relationship you may then be able to show whether or not you were really measuring propagation rather than prediction. Otherwise folks like me (and I'm guessing some of the others here who've spoken up and plenty of others like them) are going to continue to point to the known prediction mechanisms as the far more likely explanation of your results rather than grandiose claims of exceeding c. > William > > >> On 3/24/2010 4:56 PM, WWalker wrote: >>> Eric, >>> >>> The dicontinuity of a pulse from a dipole source propagates at light > speed, >>> but the pulse distorts in the nearfield because it is wideband and the >>> dispersion is not linear over the bandwidth of the signal. In the > farfield >>> the pulse realigns and propagates with out distortion at the speed of >>> light. Group speed only has meaning if the signal does not distort as > it >>> propagates. So in the nearfield one can not say anything about the >>> propagation speed of a pulse, but in the farfield the pulse clearly >>> propagates undistorted at the speed of light. >> >> In previous posts you seemed to be claiming that the signal was >> propagating faster than c in the near field. Now you are saying "in >> the nearfield one can not say anything about the propagation speed of a >> pulse". Can you clear up my confusion? Are you claiming that there is >> a region over which the signal propagates at a speed faster than c? >> >>> Only a narrowband signal propagates without distortion in both the >>> nearfield and farfield from a dipole source. This is because the > dispersion >>> is not very nonlinear and can approximately linear over the bandwidth of > a >>> narrow band signal. Since the signal does not distort as it propagates > then >>> the group speed can be clearly observed. >> >>> The dipole system is not a filter. Wave propagation from a dipole > source >>> occurs in free space. There is not a medium which can filter out or > change >>> frequency components in a signal. The transfer functions of a dipole > source >>> simply decribes how the field components propagate. >> >> Dipoles are actually bandpass filters with a center frequency determined >> by the length of the dipole as related to the wavelength of the carrier. >> Efficiency drops off significantly as the wavelength changes >> substantially from the resonant length of the dipole. >> >>> Clearly simple narrowband AM radio transmission contains information. > Just >>> turn on an AM radio and listen. The information is known to be the >>> modulation envelope of the AM signal. My simmulation simply shows that > in >>> the nearfield, the modulation envelope arrives earlier in time (dt) than > a >>> light speed propagated modulation (dt=0.08/fc), where fc is the carrier >>> frequency. >> >> You seem to be unclear on the definition of "information" in this >> context, and I think it's a big part of what's tripping you up. The AM >> radio broadcast signals you like to cite contain "information" because >> they're modulated with a significant degree of random components. As >> has been pointed out previously, you may not have an adequate grasp on >> what "random" means in this context, either. So not getting >> "information" and "random" right in this context may be the root of >> what's led you astray. >> >> I shall point out again, as have others, that if you introduce some >> genuine randomness (i.e., information) into your test signals you will >> be able to demonstrate whether your claims of propagation faster than c >> are true (if you are, in fact, still claiming that) or not. Until then >> I will again point out that your current test signals are NOT adequate >> for that purpose. Jerry pointed out long ago that your signals are >> completely deterministic, and, therefore, not random. Anybody with the >> most basic knowledge of trigonometry can predict the exact value of the >> signal at ANY point in the future given the initial parameters. In >> fact, your simulation can do that, too! And it is! That proves >> absolutely nothing and does not support the claims that you have been >> making of propagation faster than the speed of light. >> >> The same can not be said of a typical AM radio broadcast signal because >> those do, in fact, have random components due to the changing nature of >> the modulating signals. The parameters of your modulating signals, the >> amplitudes and relative phases of the initial input sinusoids, do not >> change and therefore carry no information beyond those initial >> parameters. This means that a short window of observation is all that >> is needed to extract what little information there is in the signal, >> because there isn't any additional information added beyond that. >> After that, no information is carried in the signal other than "no >> change", and there certainly aren't any random components by which to >> measure information propagation. >> >> A static '1' has minimal information, and observing it's state past >> reliable detection of the initial transition into that state will reveal >> no additional information by which propagation speed can be measured. >> This is the case with your test signals as well. The relative phases of >> the signals are NOT indicative of propagation velocity. You need to add >> a perturbation of some sort, i.e., new modulating information, and >> detect the propagation velocity of that new modulated information. >> Until you do that it appears to me that you have no basis on which to >> make claims of any unexpected phenomena. >> >> >> >>> >>> William >>> >>> >>>> On 3/24/2010 8:04 AM, WWalker wrote: >>>>> Eric, >>>>> >>>>> There is fundamental difference between a phase shift caused by a >>> filter >>>>> and a time delay caused by wave propagation across a region of space. >>> The >>>>> Op Amp filter circuit is simply phase shifting the harmonic > components >>> of >>>>> the signal such that the overall signal appears like it has arrived >>> before >>>>> it was transmitted. The circuit is not really predicting the signal > it >>> is >>>>> only phase shifting it. >>>> >>>> Yes, this is fundamental. Still, of note, is that the way to >>>> distinguish between such a phase shift and an increase in propagation >>>> velocity is to introduce a perturbation, as Andor did, so that it can > be >>>> seen whether the prediction is due to negative group delay or >>>> accelerated propagation. Andor's experiment is revealing in that it >>>> offers a method to demonstrate that what appears to be accelerated >>>> propagation is really narrow-band prediction. As far as I can tell > you >>>> have not yet done the same, and are instead claiming the rather >>>> grandiose explanation of virtual photons (which cannot be used in the >>>> context of information transfer) and propagation faster than the speed >>>> of light. >>>> >>>> It could be cleared up pretty easily by demonstrating actual > information >>>> transmission, but it seems to me that you resort to hand waving > instead. >>>> >>>>> In my system, the time delay of the signal is completely due to wave >>>>> propagation across space. It is not a filter. >>>> >>>> You have not yet demonstrated that. >>>> >>>>> The simulation I presented simply shows the time delay of the > modulation >>> of >>>>> an AM signal transmission between two nearfield dipole antennas. If > you >>>>> zoom in one can see that the modulations arrive earlier than a light >>>>> propagated signal. >>>> >>>> Except that with the signals you're using the propagation cannot be >>>> distinguished from a phase shift. Again, the point of Andor's paper > is >>>> that there's a simple way to distinguish the difference. Until you > do >>>> so you should not expect much respect of your grandiose claims when >>>> there's a much simpler explanation. >>>> >>>>> This is not phase velocity, this is group velocity i.e. time delay of >>> the >>>>> envelope. >>>>> >>>>> William >>>> >>>> It doesn't matter which it is or whether the conditions are linear so >>>> that they're the same, you haven't demonstrated that the propagation > has >>>> accelerated. Either demonstrate some actual information transmission >>>> or expect people to keep pushing back on you. You have a high burden > of >>>> proof to make the claims that you're making, but you don't seem to > want >>>> to offer anything substantial. >>>> >>>> >>>>> >>>>> >>>>> >>>>>> On 3/23/2010 6:06 PM, WWalker wrote: >>>>>>> Eric, >>>>>>> >>>>>>> Interesting article, but I don't see how it applies to my system. > The >>>>>>> system described in the paper is a bandpass filter in a feedback >>> loop, >>>>>>> where the bandpass filter phase function is altered by the > feedback. >>>>> The >>>>>>> feedback forces the endpoints of the phase to zero, creating > regions >>> of >>>>>>> possitive slope, which yield negative group delays for narrow band >>>>> signals. >>>>>>> This causes narrow band signals at the output of the circuit appear >>> to >>>>>>> arrive earlier than signals at the input of the circuit. Because > the >>>>>>> information in the signals is slightly redundant, the circuit is > able >>>>> to >>>>>>> reconstruct future parts of the signal from the present part of the >>>>>>> signal. >>>>>> >>>>>> Snipped context to allow bottom-posting. >>>>>> >>>>>> Feedback is not necessary to produce negative group delay. Here's >>>>>> another example with a passive notch filter that exhibits negative >>> group >>>>>> delay. >>>>>> >>>>>> http://www.radiolab.com.au/DesignFile/DN004.pdf >>>>>> >>>>>> It doesn't matter what's inside a black box if it has a negative > group >>>>>> delay characteristic if the transfer function is LTI. Whether >>> there's >>>>>> feedback or not in the implementation is inconsequential. Consider >>>>>> that the passive notch filter could also be implemented as an active >>>>>> circuit with feedback, and if the transfer functions are equivalent >>> they >>>>>> are functionally equivalent. This is fundamental. I don't think > the >>>>>> feedback has anything to do with it. >>>>>> >>>>>> You're argument on the redundancy, though, is spot-on. Note that, > as >>>>>> others have already pointed out multiple times, the signals you're >>> using >>>>>> in your experiment are HIGHLY redundant, so much so that they carry >>>>>> almost no information. These signals are therefore not suitable > for >>>>>> proving anything about information propagation. >>>>>> >>>>>> >>>>>>> First of all, this is a circuit which alters the phase function > with >>>>>>> respect to time and not space, as it is in my system. The phase >>> function >>>>> in >>>>>>> the circuit is not due to wave propagaton, where mine is. >>>>>> >>>>>> As far as I've been able to tell, your evidence is based on a >>>>>> simulation, in which case dimensionalities are abstractions. You > are >>>>>> not performing anything in either time or space, you're performing a >>>>>> numerical simulation. Space-time transforms are not at all unusual >>> and >>>>>> it is likely that a substitution is easily performed. Nothing has >>>>>> propagated in your simulation in either time or space. >>>>>> >>>>>>> Secondly,unlike the circuit, my system is causal. The recieved > signal >>> in >>>>> my >>>>>>> system arrives after the signal is transmitted. It just travels >>> faster >>>>> than >>>>>>> light. >>>>>> >>>>>> Uh, the circuit is causal. That was the point. >>>>>> >>>>>> You have not demonstrated that your system is causal or not causal. >>>>>> That cannot be concluded using the waveforms you show in your paper >>> due >>>>>> to the high determinism and narrow band characteristics. >>>>>> >>>>>>> Thirdly, the negative group delay in the circuit was accomplished > by >>>>> using >>>>>>> feedback which does not exist in my system. >>>>>> >>>>>> As I stated above, this is inconsequential. >>>>>> >>>>>> >>>>>>> Information (modulations) are clearly transmitted using narrowband > AM >>>>> radio >>>>>>> communication, just listen to an AM radio. The simulation I > presented >>>>>>> simply shows that random AM modulations arrive undistorted across >>> space, >>>>> in >>>>>>> the nearfield, earlier than a light speed propagated signal. >>>>>> >>>>>> Your simulation does not demonstrate that. Turn the signal off, > even >>> at >>>>>> a zero crossing if you want to minimize perturbations, and see what >>>>> happens. >>>>>> >>>>>>> Signal purturbations can not be used to measure the signal >>> propagation >>>>> in >>>>>>> the nearfield because they distort in the nearfield, and group > speed >>> has >>>>> no >>>>>>> meaning if the signal distorts as it propagates. >>>>>>> >>>>>>> William >>>>>> >>>>>> If you cannot use a perturbation (i.e., information transmission) to >>>>>> measure signal propagation then you cannot demonstrate the speed of >>>>>> information propagation. Until you can actually demonstrate >>> something >>>>>> other than phase velocity (which is NOT information transmission and >>>>>> many here have acknowledged can be faster than c, as do I), then you >>>>>> cannot make the conclusions that you are claiming. >>>>>> >>>>>> >>>>>> -- >>>>>> Eric Jacobsen >>>>>> Minister of Algorithms >>>>>> Abineau Communications >>>>>> http://www.abineau.com >>>>>> >>>> >>>> >>>> -- >>>> Eric Jacobsen >>>> Minister of Algorithms >>>> Abineau Communications >>>> http://www.abineau.com >>>> >> >> >> -- >> Eric Jacobsen >> Minister of Algorithms >> Abineau Communications >> http://www.abineau.com >> -- Eric Jacobsen Minister of Algorithms Abineau Communications http://www.abineau.com
From: Jerry Avins on 25 Mar 2010 13:12 Jerry Avins wrote: > WWalker wrote: >> Jerry, >> >> I have tested real dipole antennas using a RF Network analyser and after >> compensating for the electrical filter characteristics of the antenna, I >> get the nonlinear dispersion curves shown in my paper. The nonlinear >> dispersion is a real observable and measureable phenomina. > > I believe that. I'm not sure what you mean by nonlinear dispersion, but > I can guess. Dispersion is the dependence of velocity on frequency. A > assume that with nonlinear dispersion, the dependence relationship > departs markedly from a straight line. All the cases I know of apparent > superluminal energy velocities arise from instances of anomalous > dispersion. Upon analysis, all turn out to be apparent only. > >> Here is another paper that presents an NEC RF numerical analysis on a >> dipole and shows the nonlinear nearfield dispersion is real and >> observable: >> http://ceta.mit.edu/pier/pier.php?paper=0505121 > > Thank you. Tha abstract is interesting. I will read the gull paper when > there is more time. The title of reference 2 is noteworthy. it is "Wave > propagation faster than light," not "Information propagation faster than > light." There's a big difference. An interesting passage near the beginning of that paper: "Of course there is no mystery involved here. The pitfall, if not embarrassing at least instructive, is that ordinary plane-wave thinking is applied to a mixture of traveling and reactive fields. In this article we seek to demonstrate, by means of an elementary theoretical exercise, [68 Sten and Hujanen] that the phase velocity near sinusoidally oscillating point dipoles does indeed exceed the speed of light, without endangering the law of causality. The effect is merely a result of the transition from the quasistatic near-field, where the fields are 'in phase' with the source, to the far-field, where the field phases depart from kr by a phase angle of π/2. In the time-domain the phenomenon manifests itself as a gradual deformation, or a step by step differentiation, of the signal waveform." Jerry -- Discovery consists of seeing what everybody has seen, and thinking what nobody has thought. .. Albert Szent-Gyorgi
From: Eric Jacobsen on 25 Mar 2010 13:13 On 3/25/2010 9:01 AM, WWalker wrote: > Jerry, > > I have tested real dipole antennas using a RF Network analyser and after > compensating for the electrical filter characteristics of the antenna, I > get the nonlinear dispersion curves shown in my paper. The nonlinear > dispersion is a real observable and measureable phenomina. > > Here is another paper that presents an NEC RF numerical analysis on a > dipole and shows the nonlinear nearfield dispersion is real and > observable: > http://ceta.mit.edu/pier/pier.php?paper=0505121 > > William FWIW, a quick read of that paper seems to support exactly what Jerry and I and others have been saying. The phase response of the near-field makes it behave similarly to a filter with negative group delay. The author even points this out about Fig. 2b, where the pulse appears to accelerate. It is not at all hard to believe that dispersion that leads to apparent non-causal behavior in passive or active filters could also seem to appear as signal propagation faster than c. >> Eric Jacobsen wrote: >> >> ... >> >>> Dipoles are actually bandpass filters with a center frequency determined > >>> by the length of the dipole as related to the wavelength of the carrier. > >>> Efficiency drops off significantly as the wavelength changes >>> substantially from the resonant length of the dipole. >> >> Herein lies the fallacy that is at the heart of what I see as self >> deception. Eric describes a real dipole, while Walter's simulation is >> constructed around an ideal one. An ideal dipole is a limit as the >> length of a real dipole goes to zero while the power it radiates remains >> constant. (Compare to an impulse: a pulse whose width goes to zero while >> its area remains constant.) Such abstractions are useful for brushing >> aside irrelevant details while retaining relevant relationships. They >> remain useful only so long as the ignored details remain irrelevant. For >> example, it is inappropriate to inquire about the voltage gradient along >> an ideal diode. >> >> An example might clarify the limit of an abstraction's utility. Consider >> a ball bouncing on a flat surface, such that every bounce's duration is >> 90% of that of the previous bounce. The ball is initially dropped from >> such a height that the first bounce lasts exactly one second. It is not >> difficult to show that the ball will come to rest after ten seconds. In >> that interval, how many times will the ball bounce? >> >> In dipoles, the extents of the near field are related to the dimensions >> of the dipole. We can expect an ideal dipole, having zero length, to >> have a very peculiar calculated near field. >> >> ... >> >> Jerry >> -- >> Discovery consists of seeing what everybody has seen, and thinking what >> nobody has thought. .. Albert Szent-Gyorgi >> ����������������������������������������������������������������������� >> -- Eric Jacobsen Minister of Algorithms Abineau Communications http://www.abineau.com
From: glen herrmannsfeldt on 25 Mar 2010 15:25 Eric Jacobsen <eric.jacobsen(a)ieee.org> wrote: > On 3/24/2010 8:04 AM, WWalker wrote: >> There is fundamental difference between a phase shift caused by a filter >> and a time delay caused by wave propagation across a region of space. The >> Op Amp filter circuit is simply phase shifting the harmonic components of >> the signal such that the overall signal appears like it has arrived before >> it was transmitted. The circuit is not really predicting the signal it is >> only phase shifting it. > Yes, this is fundamental. Still, of note, is that the way to > distinguish between such a phase shift and an increase in propagation > velocity is to introduce a perturbation, as Andor did, so that it can be > seen whether the prediction is due to negative group delay or > accelerated propagation. Well, for a narrow-band signal you are somewhat limited on the kind of perturbations you can make and still be narrow band. Getting to most signal inside a given band, though, is the reason why we have so many complicated modulation methods. > Andor's experiment is revealing in that it > offers a method to demonstrate that what appears to be accelerated > propagation is really narrow-band prediction. As far as I can tell you > have not yet done the same, and are instead claiming the rather > grandiose explanation of virtual photons (which cannot be used in the > context of information transfer) and propagation faster than the speed > of light. I believe that this has actually been done as an optics problem. There are materials that, for an appropriate input signal, can appear to generate the output faster than it should be able to get there. It is, as you say, related to the predictability of the signal. > It could be cleared up pretty easily by demonstrating actual information > transmission, but it seems to me that you resort to hand waving instead. Well, it is more complicated in the near field case. For one, it is harder to know what distance to use. The size of the antenna is very important. But also near field isn't very useful for sending signals long distances. If you increase the wavelength (to increase the range of near-field) then you necessarily go to lower carrier and lower modulation frequencies. -- glen
From: glen herrmannsfeldt on 25 Mar 2010 15:38
Jerry Avins <jya(a)ieee.org> wrote: > Eric Jacobsen wrote: >> Dipoles are actually bandpass filters with a center frequency determined >> by the length of the dipole as related to the wavelength of the carrier. >> Efficiency drops off significantly as the wavelength changes >> substantially from the resonant length of the dipole. > Herein lies the fallacy that is at the heart of what I see as self > deception. Eric describes a real dipole, while Walter's simulation is > constructed around an ideal one. An ideal dipole is a limit as the > length of a real dipole goes to zero while the power it radiates remains > constant. (Compare to an impulse: a pulse whose width goes to zero while > its area remains constant.) Such abstractions are useful for brushing > aside irrelevant details while retaining relevant relationships. They > remain useful only so long as the ignored details remain irrelevant. For > example, it is inappropriate to inquire about the voltage gradient along > an ideal diode. In addition, real dipoles have width and/or depth. (Usually rods of some radius and length.) The radius affects the resonance. When measuring the distance from a real dipole, with length, width, and depth, and in near field, what points do you measure between? > In dipoles, the extents of the near field are related to the dimensions > of the dipole. We can expect an ideal dipole, having zero length, to > have a very peculiar calculated near field. -- glen |