How to get envelope from AM signal without phase shift
in [DSP]
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From: Jerry Avins on 23 Mar 2010 16:15 WWalker wrote: > Steve, > > The only thing one has to do to prove that information can be propagated > faster than light, is to simply demonstate it. The simulation below clearly > denonstrates that this is possible. Check it for yourself. Simply copy and > paste it into Mathematica. That's not the only thing. You also have to show that the demonstration is about information. Yours is not. > The simulation generates a random modulated 100ns span signal by adding a > 50MHz,1V Peak Cosine to a 22.7MHz, 1.7V peak Cosine. Then the Modulation is > multiplied with 500MHz, 1V peak Cosine carrier. The reference envelope is > extracted by dividing by the carrier. That is deterministic, not random. Once the waveform starts, you can announce what it will be tomorrow. No information at all! ... > Finally the envelopes are plotted and a zoom of the plot clearly shows that > the information (modulation envelope) arrives earlier than a light speed > propagated signal. You knew -- or should have known -- before submitting anything to mathematical analysis what the outcome would be. There *is* no information. Jerry -- Discovery consists of seeing what everybody has seen, and thinking what nobody has thought. .. Albert Szent-Gyorgi �����������������������������������������������������������������������
From: Jerry Avins on 23 Mar 2010 16:41 WWalker wrote: > Jerry, > > AM radio stations transmit narrow band information signals every day, just > turn on an AM radio and listen. Clearly narrow band signals can carry > information. The limited bandwidth of AM channels limits their information capacity. Knowing the two-sided bandwidth of such a channel is 5 KHz should tell you that the envelope amplitudes only 100 microseconds apart will be highly correlated. The envelope amplitude 100 microseconds hence will br highly correlated with what it is now. That's prediction. > The information in an AM signal is the modulation and propagates at the > group speed. This is what I am saying propagates faster than light in the > nearfield. You see the same effect with narrow-band signals undergoing anomalous dispersion. The group (but not the energy) velocity exceeds that of light. > In my simulations I generated a random signal by adding two Cosines with > different amplitudes and frequencies, which are not harmonic. This > modulation is then multiplied with a higher frequency Cosine carrier and > the signals are sent 20 cm across space through a light speed transfer > function and an electric dipole transfer functon. The envelopes are then > detected by dividing by the carrier and the envelopes are compared. The > results clearly show that the modulation envelope from the dipole arrives > earlier than the light speed propagated envelope. What is random about something described by such simple mathematics? Jerry -- Discovery consists of seeing what everybody has seen, and thinking what nobody has thought. .. Albert Szent-Gyorgi �����������������������������������������������������������������������
From: Jerry Avins on 23 Mar 2010 16:43 Jerry Avins wrote: > WWalker wrote: >> Jerry, >> >> AM radio stations transmit narrow band information signals every day, >> just >> turn on an AM radio and listen. Clearly narrow band signals can carry >> information. > > The limited bandwidth of AM channels limits their information capacity. > Knowing the two-sided bandwidth of such a channel is 5 KHz should tell > you that the envelope amplitudes only 100 microseconds apart will be > highly correlated. The envelope amplitude 100 microseconds hence will br > highly correlated with what it is now. That's prediction. > >> The information in an AM signal is the modulation and propagates at the >> group speed. This is what I am saying propagates faster than light in the >> nearfield. > > You see the same effect with narrow-band signals undergoing anomalous > dispersion. The group (but not the energy) velocity exceeds that of light. > >> In my simulations I generated a random signal by adding two Cosines with >> different amplitudes and frequencies, which are not harmonic. This >> modulation is then multiplied with a higher frequency Cosine carrier and >> the signals are sent 20 cm across space through a light speed transfer >> function and an electric dipole transfer functon. The envelopes are then >> detected by dividing by the carrier and the envelopes are compared. The >> results clearly show that the modulation envelope from the dipole arrives >> earlier than the light speed propagated envelope. > > What is random about something described by such simple mathematics? See also http://pre.aps.org/abstract/PRE/v65/i3/e036608 > Jerry -- Discovery consists of seeing what everybody has seen, and thinking what nobody has thought. .. Albert Szent-Gyorgi �����������������������������������������������������������������������
From: glen herrmannsfeldt on 23 Mar 2010 17:09 Jerry Avins <jya(a)ieee.org> wrote: > WWalker wrote: >> The only thing one has to do to prove that information can be propagated >> faster than light, is to simply demonstate it. The simulation below clearly >> denonstrates that this is possible. Check it for yourself. Simply copy and >> paste it into Mathematica. > That's not the only thing. You also have to show that the demonstration > is about information. Yours is not. There are some interesting things that can be done in near field. One is the near field microscope, which can resolve details much smaller than the wavelength of light used. As for information transfer, there are materials with a group velocity higher than C at certain frequencies. In the usual case, you still can't transfer information faster than C through such materials. One reason is that they have strong absorption at that point, but for near field maybe that isn't so bad. In general, though, useful communication is far field. The ability to transfer, say, one bit/second over a short distance, in slightly less the d/c isn't useful. -- glen
From: glen herrmannsfeldt on 23 Mar 2010 17:18
Eric Jacobsen <eric.jacobsen(a)ieee.org> wrote: > Actually, bottom posting is the preferred method, since a single entry > can be read logically in order. I'm top-posting here just because > mixing top and bottom is worse than top posting. Personally, I am not against top posting given two conditions: First, and most important, no likely follow-ups should be expected. If someone just says "I agree", or "me, too", then there really isn't much else to say. (Me, three?) Second, is that the normal place for the follow-up material is many pages down. Of course, one should do appropriate snipping, and some people don't do that. If there is no new material in the first few pages, I am likely to just go on to the next post. In the case that someone does need to follow-up such a post, often the best thing is to snip away everything following the new post and reply just to that. That works about as well as anything else, especially if the follow-up isn't really related to the previous post. (Or often it is indirectly related, but that isn't relevant to later posts.) -- glen |