Rune Allnor wrote: ...> The spatial phase you talk about should be measured at 550 MHz, > which is the signal that actually propagates down the physical > channel.From what has been written, the signal is ordinary double-sideband AM. Make that 450 *and* 550 MHz, as I wrote at 10:04 (my time). ... Jerry -- Discovery consists of seeing what everybody has seen, and thinking what nobody has thought. .. Albert Szent-Gyorgi �����������������������������������������������������������������������
How to get envelope from AM signal without phase shift
Started by ●March 7, 2010
Reply by ●March 22, 20102010-03-22
Reply by ●March 22, 20102010-03-22
On 22 Mar, 16:14, Jerry Avins <j...@ieee.org> wrote:> Rune Allnor wrote: > > � �... > > > The spatial phase you talk about should be measured at 550 MHz, > > which is the signal that actually propagates down the physical > > channel. > > �From what has been written, the signal is ordinary double-sideband AM.I didn't catch that SSB have been ruled out.> Make that 450 *and* 550 MHz,Agreed. Rune
Reply by ●March 22, 20102010-03-22
Hi, I agree with what you have said except I have my doubts about using cross correlation.>The phase shift of the *demodulated* 50 MHz signal depends on >all kinds of details in the demodulating system, details you >have no way of knowing with sufficient accuracy. > >Again: The only way you *might* come close, is to measure both >the input and output, run both through as similar processing >stages as possible (watch out for effects of variables in >the physical implementations!) and then run a cross correlation >analysis.I do not see how to use the cross correlation to get the modulation delay. When I tried to cross correlate the input AM signal with the output AM signal (both sinusoidally modulated) I got a modulated triangular signal, where the triangle peak should be the Time Span of the windowed data plus the modulation time delay. Unfortunatly the peak of the triangle is not directly available. One has to extract the envelope of the modulated correlation signal to be able to determine the triangle peak, which is similar to what I have been trying to do with other techniques.>And again: You haven't said anything about *why* you want to >do this. Relying on phase meaurements is very poor way of doing >anything. There is almost certainly a better way of doing >whatever it is you are up to. >I want to show that information propagates faster than light in the nearfield of a dipole source. Network analyser measurments between dipole antennas show that the phase is nonlinear in the nearfield and only linear in the farfield. Analysis of the phase vs freq curve shows that the group speed is faster than light in the nearfield. Refer to p. 25-26 of my paper: http://xxx.lanl.gov/pdf/physics/0603240 William
Reply by ●March 22, 20102010-03-22
WWalker wrote:> Hi, I agree with what you have said except I have my doubts about using > cross correlation. > >> The phase shift of the *demodulated* 50 MHz signal depends on >> all kinds of details in the demodulating system, details you >> have no way of knowing with sufficient accuracy. >> >> Again: The only way you *might* come close, is to measure both >> the input and output, run both through as similar processing >> stages as possible (watch out for effects of variables in >> the physical implementations!) and then run a cross correlation >> analysis. > > I do not see how to use the cross correlation to get the modulation delay. > When I tried to cross correlate the input AM signal with the output AM > signal (both sinusoidally modulated) I got a modulated triangular signal, > where the triangle peak should be the Time Span of the windowed data plus > the modulation time delay. Unfortunatly the peak of the triangle is not > directly available. One has to extract the envelope of the modulated > correlation signal to be able to determine the triangle peak, which is > similar to what I have been trying to do with other techniques. > > >> And again: You haven't said anything about *why* you want to >> do this. Relying on phase meaurements is very poor way of doing >> anything. There is almost certainly a better way of doing >> whatever it is you are up to. >> > > I want to show that information propagates faster than light in the > nearfield of a dipole source. Network analyser measurments between dipole > antennas show that the phase is nonlinear in the nearfield and only linear > in the farfield. Analysis of the phase vs freq curve shows that the group > speed is faster than light in the nearfield. Refer to p. 25-26 of my > paper: > http://xxx.lanl.gov/pdf/physics/0603240I think I have sad news for you. If faster-than-light information propagation were implemented in a general way, the future could be foretold. While we cannot foretell the future, we can predict it with more or less success. In particular, band-limited signals can be predicted quite accurately. That makes it possible to create scenarios that appear to foretell. As soon as the restriction on bandwidth is lifted, these apparent paradoxes resolve themselves. I believe it was Andor Bariska who posted striking demonstration of this. Jerry -- Discovery consists of seeing what everybody has seen, and thinking what nobody has thought. .. Albert Szent-Gyorgi �����������������������������������������������������������������������
Reply by ●March 22, 20102010-03-22
On 22 Mar, 16:30, "WWalker" <william.walker@n_o_s_p_a_m.imtek.de> wrote:> Hi, I agree with what you have said except I have my doubts about using > cross correlation. > > >The phase shift of the *demodulated* 50 MHz signal depends on > >all kinds of details in the demodulating system, details you > >have no way of knowing with sufficient accuracy. > > >Again: The only way you *might* come close, is to measure both > >the input and output, run both through as similar processing > >stages as possible (watch out for effects of variables in > >the physical implementations!) and then run a cross correlation > >analysis. > > I do not see how to use the cross correlation to get the modulation delay. > When I tried to cross correlate the input AM signal with the output AM > signal (both sinusoidally modulated) I got a modulated triangular signal, > where the triangle peak should be the Time Span of the windowed data plus > the modulation time delay. Unfortunatly the peak of the triangle is not > directly available. One has to extract the envelope of the modulated > correlation signal to be able to determine the triangle peak, which is > similar to what I have been trying to do with other techniques. � �Cross correlation gets you the phase delay you want. All you need, is to understand what you are up to, how the methods work, the error sources and how to atually do the analysis. Get the Bendat and Piersol book.> >And again: You haven't said anything about *why* you want to > >do this. Relying on phase meaurements is very poor way of doing > >anything. There is almost certainly a better way of doing > >whatever it is you are up to. > > I want to show that information propagates faster than light in the > nearfield of a dipole source. Network analyser measurments between dipole > antennas show that the phase is nonlinear in the nearfield and only linear > in the farfield. Analysis of the phase vs freq curve shows that the group > speed is faster than light in the nearfield. Refer to p. 25-26 of my > paper:http://xxx.lanl.gov/pdf/physics/0603240Ouch... well, you claim affiliations with NTNU, so what would one expect... you wouldn't happen to be aware of the "Hjernevask" reports by Harald Eia, who is aired on NRK1 these days? This projects fits straight in there. You need to be *extremely* cautious about what you are up to. The stuff you are measuring is interference effects between spherical waves, *not* the propagation of energy. It is very easy to obtain infinite phase speeds in the case of plane waves: A plane wave, in the ocean, that impinges perpendiculary to a beach will exhibit an infinite phase speed along the beach. The apparent wavelength is infinitely long, so the apparent wave speed (phase velosity) is infinite. But the velocity of information down the lenght of the beach is 0. Whatever it is you *think* you measure, similar effects are in play. Check out the writings of Johan Leander in the Journal of the Acoustical Society of America, in 1995 or 1996. Rune
Reply by ●March 22, 20102010-03-22
Rune Allnor <allnor@tele.ntnu.no> wrote:> On 22 Mar, 00:48, glen herrmannsfeldt <g...@ugcs.caltech.edu> wrote:>>?After a signal goes through a dispersive >> medium (such as optical fiber), it then goes through a phase >> conjugation device. ?That reverses the effect such that passing >> through the same amount of fiber restores the original signal. >> That is, dispersive fiber+phase conjugation+dispersive fiber >> is, overall, not dispersive!> I remember reading some time in the mid / late '90s about a phase > conjugation tecnique used in a multipath scenario, in the context > of active sonars. Since phase conjugation in time domain amounts > to time reversal, these guys suggested toI understand phase conjugation for optical systems better, but...> 1) Emit a known waveform into the water > 2) Record the echo reflected off the target (which suffers from > reverberation, multipath and what not) > 3) Reverse the recorded signal and emit > 4) Record the reflection from the time-reversed recordingThe main thing this depends on is that conditions don't change (too much) between the two emission times. For time reversal, you can't start sending the time reversed signal until all of the first one is received. For optics, that time is related to the size of the phase conjugation device.> I never understood what the purpose of all this might have > been.In 'standard mode' there are all kinds of problems > detecting the reflection of interest inbetween all the > multipaths and distortions. If you already know these > factors, you also know the reference time around which > to flip the signal.I will guess that temperature gradients are part of the cause of dispersion. Presumably they change with time as currents move the water around.> If you are unable to untangle the recieved signal, you don't > know the key references, and effectively emit a random signal. > Even if the idea works, and you recieve something that is close > to the original pulse, you have no idea which part of the > emitted signal interacted with the target.Well, that problem is always there.> In the end, one have spent an awful lot of effort for no > gain at all.-- glen
Reply by ●March 22, 20102010-03-22
Hi Rune, Although the cross correlation method could perhaps be used to measure the time delay of the modulation, this still does not help me. I want to extract the modulation from the signal and show that it can be done in less than a fraction (<1/10) of a carrier cycle. Dividing by the carrier does this but the required SNR is too high to be practical. Transmitting Q=A(t)Sin(Wct)and I=A(t)Cos(Wct)through the antennas and demodulating using A(t)=Sqrt[I^2 + Q^2] also works. But I was hoping to find a method to extract the modulation using only one signal, such as: A(t)Sin(Wct) Any ideas? William>On 22 Mar, 16:30, "WWalker" <william.walker@n_o_s_p_a_m.imtek.de> >wrote: >> Hi, I agree with what you have said except I have my doubts about using >> cross correlation. >> >> >The phase shift of the *demodulated* 50 MHz signal depends on >> >all kinds of details in the demodulating system, details you >> >have no way of knowing with sufficient accuracy. >> >> >Again: The only way you *might* come close, is to measure both >> >the input and output, run both through as similar processing >> >stages as possible (watch out for effects of variables in >> >the physical implementations!) and then run a cross correlation >> >analysis. >> >> I do not see how to use the cross correlation to get the modulationdelay=>. >> When I tried to cross correlate the input AM signal with the output AM >> signal (both sinusoidally modulated) I got a modulated triangularsignal,>> where the triangle peak should be the Time Span of the windowed dataplus>> the modulation time delay. Unfortunatly the peak of the triangle is not >> directly available. One has to extract the envelope of the modulated >> correlation signal to be able to determine the triangle peak, which is >> similar to what I have been trying to do with other techniques. =A0 =A0 > >Cross correlation gets you the phase delay you want. >All you need, is to understand what you are up to, how >the methods work, the error sources and how to atually >do the analysis. > >Get the Bendat and Piersol book. > >> >And again: You haven't said anything about *why* you want to >> >do this. Relying on phase meaurements is very poor way of doing >> >anything. There is almost certainly a better way of doing >> >whatever it is you are up to. >> >> I want to show that information propagates faster than light in the >> nearfield of a dipole source. Network analyser measurments betweendipole>> antennas show that the phase is nonlinear in the nearfield and onlylinea=>r >> in the farfield. Analysis of the phase vs freq curve shows that thegroup>> speed is faster than light in the nearfield. Refer to p. 25-26 of my >> paper:http://xxx.lanl.gov/pdf/physics/0603240 > >Ouch... well, you claim affiliations with NTNU, so what >would one expect... you wouldn't happen to be aware of the >"Hjernevask" reports by Harald Eia, who is aired on NRK1 >these days? This projects fits straight in there. > >You need to be *extremely* cautious about what you are up to. >The stuff you are measuring is interference effects between >spherical waves, *not* the propagation of energy. It is very >easy to obtain infinite phase speeds in the case of plane waves: >A plane wave, in the ocean, that impinges perpendiculary to a >beach will exhibit an infinite phase speed along the beach. >The apparent wavelength is infinitely long, so the apparent >wave speed (phase velosity) is infinite. But the velocity >of information down the lenght of the beach is 0. > >Whatever it is you *think* you measure, similar effects >are in play. Check out the writings of Johan Leander in >the Journal of the Acoustical Society of America, in 1995 >or 1996. > >Rune >
Reply by ●March 22, 20102010-03-22
Hi Rune, What ever the the reason for this phenomina, given the known and excepted transfer function of a dipole source, It should be possible to transmit information faster than light by transmitting an AM signal in the nearfield and decoding the modulation. Simmulations clearly show that the envelope of an AM signal will arrive faster than light and undistorted in the nearfield. What is needed now is to find a way to decode the modulation within a fraction of (<1/10) a carrier cycle.>You need to be *extremely* cautious about what you are up to. >The stuff you are measuring is interference effects between >spherical waves, *not* the propagation of energy. It is very >easy to obtain infinite phase speeds in the case of plane waves: >A plane wave, in the ocean, that impinges perpendiculary to a >beach will exhibit an infinite phase speed along the beach. >The apparent wavelength is infinitely long, so the apparent >wave speed (phase velosity) is infinite. But the velocity >of information down the lenght of the beach is 0. > >Whatever it is you *think* you measure, similar effects >are in play. Check out the writings of Johan Leander in >the Journal of the Acoustical Society of America, in 1995 >or 1996. > >Rune >
Reply by ●March 22, 20102010-03-22
WWalker wrote:> Hi Rune, > > Although the cross correlation method could perhaps be used to measure the > time delay of the modulation, this still does not help me. I want to > extract the modulation from the signal and show that it can be done in less > than a fraction (<1/10) of a carrier cycle. Dividing by the carrier does > this but the required SNR is too high to be practical. Transmitting > Q=A(t)Sin(Wct)and I=A(t)Cos(Wct)through the antennas and demodulating using > A(t)=Sqrt[I^2 + Q^2] also works. But I was hoping to find a method to > extract the modulation using only one signal, such as: A(t)Sin(Wct) > > Any ideas?You just don't pay attention to what's being said to you. I can't help you, so I'll stop trying. Jerry -- Discovery consists of seeing what everybody has seen, and thinking what nobody has thought. .. Albert Szent-Gyorgi �����������������������������������������������������������������������
Reply by ●March 22, 20102010-03-22
On 22 Mar, 22:43, "WWalker" <william.walker@n_o_s_p_a_m.imtek.de> wrote:> Hi Rune, > > What ever the the reason for this phenomina, given the known and excepted > transfer function of a dipole source, It should be possible to transmit > information faster than light by transmitting an AM signal in the nearfield > and decoding the modulation. Simmulations clearly show that the envelope of > an AM signal will arrive faster than light and undistorted in the > nearfield. What is needed now is to find a way to decode the modulation > within a fraction of (<1/10) a carrier cycle.Wrong. Your simulations use fixed-parameter sinusoidals and have as such nothing to do with information, only steady states. Everything is known all the time; there is nothing new to be learned from observing the wave field. Hence, no information is transmitted. If you want to transmit *information*, you need to change something in the wavefield: The amplitude, the frequency or the phase. Something that is not known, that the reciever has to lock on to, detect and quantify. It is this *transient* change to an *unknown* state that carries the information down range between transmitter and reciever. I can guarantee that you will find that the transients propagate down range with a speed exactly equal to c. Rune
