EM pulse detection
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Posted by on September 15, 2008, 8:54 am
Please log in for more thread options EM pulse detection Is it possible to measure with great precision the time at which a very short EM pulse reaches a receiver situated at some distance from the emitter? The time should be recorded on the emitter's clock and also on the receiver's clock. Thank you very much, Marcel Luttgens | |||||||||||||||||||||||||||||||||||||
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Posted by Jon Slaughter on September 15, 2008, 9:17 am
Please log in for more thread options If you have ideal measuring devices you can! The error is going be in generating the pulse and recieving it(assuming any dispersion is irrelevant). It think you need to give more information about such things as in general the lower the frequency the less well defined a "pulse" is. (i.e., a square wave pulese has infinite frequency and is "exact" but a sinewave has one frequency and is inexact) You might combine different methods of testing and such but you need to determine what "great precision" is and how you can calibrate your system to check your "great precision". I think your question is just to general to get any specific answer. | |||||||||||||||||||||||||||||||||||||
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Posted by on September 15, 2008, 11:07 am
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>
> > > EM pulse detection
>
> > Is it possible to measure with great precision the time
> > at which a very short EM pulse reaches a receiver situated > > at some distance from the emitter? > > The time should be recorded on the emitter's clock and > > also on the receiver's clock. >
l
> If you have ideal measuring devices you can! The error is going be in > generating the pulse and recieving it(assuming any dispersion is > irrelevant). > > It think you need to give more information about such things as in genera= > the lower the frequency the less well defined a "pulse" is. (i.e., a squa=
re
> wave pulese has infinite frequency and is "exact" but a sinewave has one
to
> frequency and is inexact) > > You might combine different methods of testing and such but you need to > determine what "great precision" is and how you can calibrate your system= > check your "great precision".
> > I think your question is just to general to get any specific answer. Thank you for your remarks The aim is to measure the speed of light. I don't know if there are devices having the required precision. Marcel Luttgens | |||||||||||||||||||||||||||||||||||||
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Posted by Jon Slaughter on September 15, 2008, 4:56 pm
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>
> > > EM pulse detection
>
> > Is it possible to measure with great precision the time
> > at which a very short EM pulse reaches a receiver situated > > at some distance from the emitter? > > The time should be recorded on the emitter's clock and > > also on the receiver's clock. >
> If you have ideal measuring devices you can! The error is going be in > generating the pulse and recieving it(assuming any dispersion is > irrelevant). > > It think you need to give more information about such things as in general > the lower the frequency the less well defined a "pulse" is. (i.e., a > square > wave pulese has infinite frequency and is "exact" but a sinewave has one > frequency and is inexact) > > You might combine different methods of testing and such but you need to > determine what "great precision" is and how you can calibrate your system > to > check your "great precision". > > I think your question is just to general to get any specific answer. Thank you for your remarks The aim is to measure the speed of light. I don't know if there are devices having the required precision. Marcel Luttgens ------- Is their any specific reason why? It is well known that c = 299792458 m/s. Chances are you'll be better off using indirect methods http://en.wikipedia.org/wiki/Speed_of_light I really don't see any reason why you would want to measure the speed of light as it has already been done and probably to a much greater precision then you will ever be able to do by yourself. | |||||||||||||||||||||||||||||||||||||
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Posted by extremesoundandlight@yahoo.com on September 15, 2008, 11:36 am
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On Sep 15, 5:54=C2=A0am, mluttg...@wanadoo.fr wrote: > EM pulse detection
> > Is it possible to measure with great precision the time > at which a very short EM pulse reaches a receiver situated > at some distance from the emitter? > The time should be recorded on the emitter's clock and > also on the receiver's clock. > > Thank you very much, > > Marcel Luttgens is the receiver situated at some distance from the emitter with a rough terrain or or smooth you can use this formula if you modulate two separate frequecies of coherent light with an Em frequency over any terrain at any distance =E2=88=87=E2=80=B22=CF=88(x=E2=80=B2, z=E2=80=B2, =CF=89) + k2(=CF=89)n2=CF= =88(x=E2=80=B2, z=E2=80=B2, =CF=89) =3D 0 (1) where =CF=88 represents the field for either the vertically or horizontally polarized wave. For vertically polarized wave, =CF=88 is the magnetic field, which has component only along the y direction. For horizontally polarized wave, =CF=88 represents the electric field, which is pointed along the y direction. In addition, =E2=88=87=E2=80=B22 =3D =E2=88= =822/=E2=88=82x=E2=80=B22 + =E2=88=822/=E2=88=82z=E2=80=B22, k2(=CF=89) =3D =CF=892=C2=B50=C7=AB0, and n is the index of refraction of the propagating medium. It can be shown that many important radio wave propagation phenomena can be reduced to this twodimensional problem [3]. In two dimensions, the irregular terrain is described by the function z=E2=80=B2 =3D f(x=E2=80=B2). In this paper the terrain surfac= e profile f(x) is assumed to be a stochastic process. The problem we are concerned with is that of radio wave propagation over irregular terrain, in which a transmitter located at the horizontal position x=E2=80=B2 =3D x0 and at a height of h above ground radiates a transient pulse. The pulse then propagates in the positive x=E2=80=B2 direction until it reaches= a receiver located at the horizontal position x=E2=80=B2 =3D x, and a height of z above ground= . The geometry of the problem under consideration is shown in figure 1, where the horizontal distance between the transmitter and receiver is R. We further assume that the terrain material can be approximated by perfect electric conductors (PEC). Therefore, for vertically polarized wave, equation (1) satisfies the Neumann boundary condition, =E2=88=82=CF=88 =E2=88=82z=E2=80=B2 =0C=0C=0C=0Cz=E2=80=B2=3Df(x=E2=80=B2) =3D 0. (2) While for horizontally polarized wave, the boundary condition is given by the Dirichlet boundary condition, =CF=88|z=E2=80=B2=3Df(x=E2=80=B2) =3D 0. (3) We make the assumption that the terrain elevation varies on a scale length large compare to the wavelength of the radio wave and also that the wave propagates at small grazing angle relative to the x axis. Then, using the forward scattering approximation, | |||||||||||||||||||||||||||||||||||||
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>
> Is it possible to measure with great precision the time
> at which a very short EM pulse reaches a receiver situated
> at some distance from the emitter?
> The time should be recorded on the emitter's clock and
> also on the receiver's clock.
>