How to get envelope from AM signal without phase shift
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From: Eric Jacobsen on 24 Mar 2010 20:28 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
From: Jerry Avins on 24 Mar 2010 22:54 Eric Jacobsen wrote: ... > 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. Some people fail to distinguish between "random" and "arbitrarily chosen". That can lead to astonishing errors of analysis. ... Jerry -- Discovery consists of seeing what everybody has seen, and thinking what nobody has thought. .. Albert Szent-Gyorgi �����������������������������������������������������������������������
From: Jerry Avins on 25 Mar 2010 10:58 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 �����������������������������������������������������������������������
From: WWalker on 25 Mar 2010 12:01 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 >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 >����������������������������������������������������������������������� >
From: Jerry Avins on 25 Mar 2010 12:19
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. Jerry -- Discovery consists of seeing what everybody has seen, and thinking what nobody has thought. .. Albert Szent-Gyorgi ����������������������������������������������������������������������� |