How to get envelope from AM signal without phase shift
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From: steveu on 23 Mar 2010 22:13 >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. > Well he doesn't have to actually demonstrate a perturbation going faster than light. If he could demonstrate energy travelling faster than light, it would be equivalent. However, only one person here doesn't seem to grasp that this ain't gonna happen. Steve
From: Jerry Avins on 23 Mar 2010 23:55 WWalker wrote: ... > 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. Andor's circuit can be built from real parts. How could it not be causal? > Thirdly, the negative group delay in the circuit was accomplished by using > feedback which does not exist in my system. Negative group delay is just that, no matter how produced. Test your system with real transients. > 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. You don't seem to know what "random" really means. http://en.wikipedia.org/wiki/Randomness might help. > 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. True randomness guarantees perturbations. > William Jerry -- Discovery consists of seeing what everybody has seen, and thinking what nobody has thought. .. Albert Szent-Gyorgi �����������������������������������������������������������������������
From: Jerry Avins on 24 Mar 2010 00:02 steveu wrote: > ... only one person here doesn't seem to grasp > that this ain't gonna happen. It was the subject of his thesis and he passed his defence, so it must be valid. Isn't that how it goes? Jerry -- Discovery consists of seeing what everybody has seen, and thinking what nobody has thought. .. Albert Szent-Gyorgi �����������������������������������������������������������������������
From: Eric Jacobsen on 24 Mar 2010 10:51 On 3/23/2010 9:02 PM, Jerry Avins wrote: > steveu wrote: > >> ... only one person here doesn't seem to grasp >> that this ain't gonna happen. > > It was the subject of his thesis and he passed his defence, so it must > be valid. Isn't that how it goes? > > Jerry I'm struggling to believe that this is true. That's a pretty sad indictment of that institution if this got by a PhD committee. I suspect there's more to this story. There's a number of things that don't make sense here, beyond the obvious claims. -- Eric Jacobsen Minister of Algorithms Abineau Communications http://www.abineau.com
From: WWalker on 24 Mar 2010 11:04
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. In my system, the time delay of the signal is completely due to wave propagation across space. It is not a filter. 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. This is not phase velocity, this is group velocity i.e. time delay of the envelope. William >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 > |