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Testing superluminal transmission of near field light waves.



 
 
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  #41  
Old April 4th 07, 01:30 PM posted to sci.physics.relativity,sci.physics,sci.physics.electromag,sci.astro
William[_2_]
external usenet poster
 
Posts: 11
Default Testing superluminal transmission of near field light waves.


The RF antenna group at NTNU university has looked into your network
analyzer/balanced dipole/balun experimental setup and has preformed
tests on a similar setup. They concluded that the observed phase shift
results are unreliable due to external room reflections and that the
experiment needs to be performed in an anechoic chamber.

In their tests they used an Agilent-E8364B S parameter Network Analyzer
(10MHz-50GHz), a HP 85052D4 Calibration kit, a 30cm balanced dipole
antenna with built in Balun (500MHz resonant frequency, 60cm
wavelength), an E field probe (a 0.5m cable with about 1cm exposed
wire), 1m HF Cables with SMA connectors, 10dB attenuators (placed at the
input to the Balun/Antenna and at the output of the E field probe). A
full calibration (using the cal kit - short, load, open, thru) was
performed on the analyzer including the RF cables and attached
attenuators. The Analyser was swept from 400MHz-600MHz while monitoring
the S21 phase at 500MHz. Linear as well as nonlinear phase vs distance
relations were observed as the probe was moved from next to the dipole
to the dipole wavelength (60cm).

A 2GHz -20GHz Anechoic chamber is available here, but preliminary tests
with the antenna at 1.5GHz (3rd harmonic of antenna) showed that phase
calibration of the analyzer is not possible due to losses in the the
long cables (10m), needed to connect the antenna and probe to the
analyzer outside the chamber.

It has been recommended that a small Anechoic chamber be constructed
specially designed for this experiment, enabling the analyzer and 1m
cables to be calibrated. The chamber should include a nonreflective
mechanism enabling the probe to be moved in small repeatable increments
within the wavelength of the antenna. The new chamber will take some
time to design, build and test, and the cost could be prohibitively
expensive. During the next few weeks I will check into this possibility.



doug wrote:
William wrote:

I agree that the experiment I did should be checked, but I think it is
best to do the experiment in the lab using high frequency test equipment
like you are trying to do. As you have said the experiment is very
difficult to do right and there is a better chance of controlling all
the phenomena involved in a standard RF lab environment using commercial
test equipment. I also agree that it is essential that these
near-field measurement tests show nonlinear phase shift behavior in
the nearfield before progressing to a wide bandwidth signal
transmission experiments.

I am very surprised by your experimental results. The transverse field
phase vs distance solution I presented in my paper is what is predicted
by Maxwell's equations (p.12, near-field dipole paper). I have checked
it both analytically and numerically (p.23-25). In addition the solution
has also been checked by other researchers, analytically and numerically:
http://ceta.mit.edu/pier/pier56/05.0505121.Sten.H.pdf
http://xxx.lanl.gov/abs/physics/0311061

Intuitively one can also see the nonlinear phase shift by looking at
the transverse field solution (Eq. 53). The exp[i(kr-wt)] term is a light
speed propagating term, and the part in the brackets is a complex term
that is a function of kr. This complex term can be expressed in polar
coordinates as a phasor, where the phase will cause the over phase of
the field to deviate from kr. In the nearfield, the kr term is small
thereby making the making the term in the brackets approximately equal
to 1, corresponding to 0 deg phase difference from kr. In the farfield
the
term in the brackets becomes approximately -(kr)^2 corresponding to -180
deg phase difference from kr. In between the nearfield and the farfield
the -i(kr) term is dominant, causing the phase to be about -90 deg
there. If you will refer to the transverse Electric field phase vs kr
curve (ref. fig.12) you will see that the theoretically derived curve
agrees with these observations. Relative to a light propagating field,
the phase is 0 deg in the nearfield, approximately -90 deg in between
the nearfied and farfield, and -180 deg in the farfield.

Experimentally it is known that the E field generated by a slow moving
charge is proportional to it's position. Oscillating charges cause other
nearby charges to oscillate in unison with no observed phase difference.
In the nearfield, the B field is experimentally known to be proportional
to the current. Oscillating charges are known to generate magnetic
fields which are -90 deg phase shifted from the charge motion. In the
farfield it has been experimentally observed that the transverse
electric and magnetic fields are in phase and propagate at the speed of
light. I order for the transverse E field and B field to align in the
farfield, given that they are not aligned in the nearfield, their phase
vs distance curves must be nonlinear in the nearfield.

Do you have any ideas what the problem is? It is hard to believe that
Maxwell's equations could be wrong in the prediction of this nonlinear
phase shift effect.



The defining result is what reality thinks. After there are
reproducible experimental results, it will be the time to go through
the equations. The experiment is simple. The analysis is not and there
have been comments from others who have disagreed with your assumptions.
I am not making any assumptions about either your derivations or their
disagreements.


Until I know more exactly what you have done I can only speculate.
First of all I am extremely wary of any test that uses more than one
frequency which can generate phase shifts from band limited elements
such as the balun and antenna, or from frequency dependent
reflections. But if I understand you correctly, even though the
Analyzer is sweeping frequencies, you are effectively using only one
frequency by reading only the phase at one particular frequency as the
E field probe is moved incrementally away from the Dipole antenna. I
assume you have calibrated the Analyzer and test cables using a
calibrated short, open, and 50 ohm terminators at the end of the test
cables, thus effectively flattening out the transfer function of these
elements. I also assume the Analyzer is able to measure at least 1 deg
phase changes, which is needed to differentiate linear from nonlinear
phase behavior in the nearfield. Can the analyzer be operated at just
1 frequency just to be sure the sweeping is not causing any problems
(eg. intermode mixing etc.).

As someone who does this kind of measurement every day, I have a pretty
good idea of the limits. First of all, the hp8753 is a stepped frequency
analyzer which sets a frequency and then takes the data so you worries
about sweeping effects do not exist. I have a stack of hp calibration
kits with a large selection of loads, mismatches, opens and shorts. The
transfer function of the system is not important at a single frequency.
It is important if you are measuring frequency dependence but that is
not being done. The data were looked at at different frequencies but
the phase comparisons were done at fixed frequencies. You can look up
the specs of the 8753 family to see what the resolutions are.

By the way have you checked that the input impedance of the
probe/Analyzer combined with the antenna to probe reactance (which
changes as the probe is moved away)is not generating a phase shift
which could be masking the true phase in the nearfield?


There are 10db attenuators at the end of the antenna and the end of
the voltage probe. This isolates the cables and test set from the
changing impedances.

Could reflections from the probe be reflecting from the Dipole antenna
causing the phase shift in the nearfield to be masked?


The probe is .5" long and this effect would show up with varying lengths
of e field probes. The two probes I used showed no difference.
I would like to make these measurements with a B field probe when I get
a chance.

In order to be able to really understand your experimental results, I
will need to know more about your experimental test setup and test
results. This will also enable the duplication of your experiment.


I am really quite surprised by these comments on things that are second
or third order effects when there are problems with your measurement
that are zeroth or first order.
You have no antenna, just a voltage probe trying to radiate.
You have no impedance match anywhere.
You have not isolated the transmitter.
You have no ground plane (the table just makes life complicated)
You have a dc circuit which does not match what you think your rf
circuit is.

The important part of the measurement is to create a geometry which is
what you think it is. A dipole antenna in free space is far more
predictable than any system with a ground plane. All parts of the
system have to be isolated from each other so you are only varying
what you think you are varyings. For instance, changing the load on
most cheap rf equipment (and the hamtronics fits that category) will
cause changes in amplitude,phase and harmonic content. Once all
the parts are properly characterized and isolated, then you can vary
whatever parameter you want with confidence that it is the only one
you are changing.

When the experiment is done properly, the results will speak for
themselves. If you get different results than I do, then we need to
look for the reason for those differences. I have listed a large
number of problems with your setup. If you fix those things, we will
be in a position to compare results.



doug wrote:

William wrote:

Hi Bill,

Thank you for the offer, but I think that duplicating the type of
experiment I showed in paper would not yield much new information.
What really needs to be done is to develop a wideband transmitter
and antenna system that can handle modulations bandwidths 1/10 of
the carrier. This will enable us to study the propagation speed of
random information, which is what everyone wants to know. This is
not a trivial design and I don't even know if it can be done. I will
have to give it some thought. If I do get something to work, I will
let you know.


trimmed discussion I am not replying to

I think you have this backwards. The first thing to do is to replicate
the experiment you did. It seems you still believe it is correct. I
have given a list of mistakes you have made. With your setup, no one
with rf experience will take it seriously. I showed it to a colleague
and he laughed. The basic experiment you are basing your work on must
be done correctly and repeatably. You are not using proper antennas, you
have not impedance matched anything so you do not know what the fields
are, you do not have an infinite ground plane.... You probably are
seeing an odd field distribution from the geometry you have created.

My repeat of your experiment showed no anomalous effect on the phase.
In order to have any effect to discuss, you are required to show a
nonlinear phase with distance. I get a straight line for the phase
versus distance curve which means that there is a constant value for c
at all distances. It shows the same effect at different frequencies
so I also have the time dependence which thus also shows no anomaly.
There
is no point in doing the time domain experiment when you can do the
frequency domain experiment much more easily. They are equivalent and
can be done on the same piece of equipment.

One can build the modulator you suggest but there is no need. Again
the frequency domain is the same thanks to our friend fourier. I have
spent the last ten years designing and using frequency domain radars. If
the phase versus frequency is linear at all frequencies, there is no
effect to study.




  #42  
Old April 4th 07, 05:03 PM posted to sci.physics.relativity,sci.physics,sci.physics.electromag,sci.astro
doug
external usenet poster
 
Posts: 11
Default Testing superluminal transmission of near field light waves.

William wrote:

The RF antenna group at NTNU university has looked into your network
analyzer/balanced dipole/balun experimental setup and has preformed
tests on a similar setup. They concluded that the observed phase shift
results are unreliable due to external room reflections and that the
experiment needs to be performed in an anechoic chamber.

In their tests they used an Agilent-E8364B S parameter Network Analyzer
(10MHz-50GHz), a HP 85052D4 Calibration kit, a 30cm balanced dipole
antenna with built in Balun (500MHz resonant frequency, 60cm
wavelength), an E field probe (a 0.5m cable with about 1cm exposed
wire), 1m HF Cables with SMA connectors, 10dB attenuators (placed at the
input to the Balun/Antenna and at the output of the E field probe). A
full calibration (using the cal kit - short, load, open, thru) was
performed on the analyzer including the RF cables and attached
attenuators. The Analyser was swept from 400MHz-600MHz while monitoring
the S21 phase at 500MHz. Linear as well as nonlinear phase vs distance
relations were observed as the probe was moved from next to the dipole
to the dipole wavelength (60cm).

A 2GHz -20GHz Anechoic chamber is available here, but preliminary tests
with the antenna at 1.5GHz (3rd harmonic of antenna) showed that phase
calibration of the analyzer is not possible due to losses in the the
long cables (10m), needed to connect the antenna and probe to the
analyzer outside the chamber.

It has been recommended that a small Anechoic chamber be constructed
specially designed for this experiment, enabling the analyzer and 1m
cables to be calibrated. The chamber should include a nonreflective
mechanism enabling the probe to be moved in small repeatable increments
within the wavelength of the antenna. The new chamber will take some
time to design, build and test, and the cost could be prohibitively
expensive. During the next few weeks I will check into this possibility.



doug wrote:

William wrote:

I agree that the experiment I did should be checked, but I think it is
best to do the experiment in the lab using high frequency test equipment
like you are trying to do. As you have said the experiment is very
difficult to do right and there is a better chance of controlling all
the phenomena involved in a standard RF lab environment using commercial
test equipment. I also agree that it is essential that these
near-field measurement tests show nonlinear phase shift behavior in
the nearfield before progressing to a wide bandwidth signal
transmission experiments.

I am very surprised by your experimental results. The transverse field
phase vs distance solution I presented in my paper is what is predicted
by Maxwell's equations (p.12, near-field dipole paper). I have
checked it both analytically and numerically (p.23-25). In addition
the solution
has also been checked by other researchers, analytically and
numerically:
http://ceta.mit.edu/pier/pier56/05.0505121.Sten.H.pdf
http://xxx.lanl.gov/abs/physics/0311061

Intuitively one can also see the nonlinear phase shift by looking at
the transverse field solution (Eq. 53). The exp[i(kr-wt)] term is a
light
speed propagating term, and the part in the brackets is a complex term
that is a function of kr. This complex term can be expressed in polar
coordinates as a phasor, where the phase will cause the over phase of
the field to deviate from kr. In the nearfield, the kr term is small
thereby making the making the term in the brackets approximately
equal to 1, corresponding to 0 deg phase difference from kr. In the
farfield the
term in the brackets becomes approximately -(kr)^2 corresponding to -180
deg phase difference from kr. In between the nearfield and the farfield
the -i(kr) term is dominant, causing the phase to be about -90 deg
there. If you will refer to the transverse Electric field phase vs kr
curve (ref. fig.12) you will see that the theoretically derived curve
agrees with these observations. Relative to a light propagating field,
the phase is 0 deg in the nearfield, approximately -90 deg in between
the nearfied and farfield, and -180 deg in the farfield.

Experimentally it is known that the E field generated by a slow moving
charge is proportional to it's position. Oscillating charges cause other
nearby charges to oscillate in unison with no observed phase difference.
In the nearfield, the B field is experimentally known to be proportional
to the current. Oscillating charges are known to generate magnetic
fields which are -90 deg phase shifted from the charge motion. In the
farfield it has been experimentally observed that the transverse
electric and magnetic fields are in phase and propagate at the speed of
light. I order for the transverse E field and B field to align in the
farfield, given that they are not aligned in the nearfield, their phase
vs distance curves must be nonlinear in the nearfield.

Do you have any ideas what the problem is? It is hard to believe that
Maxwell's equations could be wrong in the prediction of this
nonlinear phase shift effect.




The defining result is what reality thinks. After there are
reproducible experimental results, it will be the time to go through
the equations. The experiment is simple. The analysis is not and there
have been comments from others who have disagreed with your assumptions.
I am not making any assumptions about either your derivations or their
disagreements.


Until I know more exactly what you have done I can only speculate.
First of all I am extremely wary of any test that uses more than one
frequency which can generate phase shifts from band limited elements
such as the balun and antenna, or from frequency dependent
reflections. But if I understand you correctly, even though the
Analyzer is sweeping frequencies, you are effectively using only one
frequency by reading only the phase at one particular frequency as
the E field probe is moved incrementally away from the Dipole
antenna. I assume you have calibrated the Analyzer and test cables
using a calibrated short, open, and 50 ohm terminators at the end of
the test cables, thus effectively flattening out the transfer
function of these elements. I also assume the Analyzer is able to
measure at least 1 deg phase changes, which is needed to
differentiate linear from nonlinear phase behavior in the nearfield.
Can the analyzer be operated at just 1 frequency just to be sure the
sweeping is not causing any problems (eg. intermode mixing etc.).

As someone who does this kind of measurement every day, I have a pretty
good idea of the limits. First of all, the hp8753 is a stepped frequency
analyzer which sets a frequency and then takes the data so you worries
about sweeping effects do not exist. I have a stack of hp calibration
kits with a large selection of loads, mismatches, opens and shorts. The
transfer function of the system is not important at a single frequency.
It is important if you are measuring frequency dependence but that is
not being done. The data were looked at at different frequencies but
the phase comparisons were done at fixed frequencies. You can look up
the specs of the 8753 family to see what the resolutions are.

By the way have you checked that the input impedance of the
probe/Analyzer combined with the antenna to probe reactance (which
changes as the probe is moved away)is not generating a phase shift
which could be masking the true phase in the nearfield?


There are 10db attenuators at the end of the antenna and the end of
the voltage probe. This isolates the cables and test set from the
changing impedances.

Could reflections from the probe be reflecting from the Dipole
antenna causing the phase shift in the nearfield to be masked?


The probe is .5" long and this effect would show up with varying lengths
of e field probes. The two probes I used showed no difference.
I would like to make these measurements with a B field probe when I get
a chance.

In order to be able to really understand your experimental results, I
will need to know more about your experimental test setup and test
results. This will also enable the duplication of your experiment.


I am really quite surprised by these comments on things that are second
or third order effects when there are problems with your measurement
that are zeroth or first order.
You have no antenna, just a voltage probe trying to radiate.
You have no impedance match anywhere.
You have not isolated the transmitter.
You have no ground plane (the table just makes life complicated)
You have a dc circuit which does not match what you think your rf
circuit is.

The important part of the measurement is to create a geometry which is
what you think it is. A dipole antenna in free space is far more
predictable than any system with a ground plane. All parts of the
system have to be isolated from each other so you are only varying
what you think you are varyings. For instance, changing the load on
most cheap rf equipment (and the hamtronics fits that category) will
cause changes in amplitude,phase and harmonic content. Once all
the parts are properly characterized and isolated, then you can vary
whatever parameter you want with confidence that it is the only one
you are changing.

When the experiment is done properly, the results will speak for
themselves. If you get different results than I do, then we need to
look for the reason for those differences. I have listed a large
number of problems with your setup. If you fix those things, we will
be in a position to compare results.



doug wrote:

William wrote:

Hi Bill,

Thank you for the offer, but I think that duplicating the type of
experiment I showed in paper would not yield much new information.
What really needs to be done is to develop a wideband transmitter
and antenna system that can handle modulations bandwidths 1/10 of
the carrier. This will enable us to study the propagation speed of
random information, which is what everyone wants to know. This is
not a trivial design and I don't even know if it can be done. I
will have to give it some thought. If I do get something to work, I
will let you know.


trimmed discussion I am not replying to

I think you have this backwards. The first thing to do is to replicate
the experiment you did. It seems you still believe it is correct. I
have given a list of mistakes you have made. With your setup, no one
with rf experience will take it seriously. I showed it to a colleague
and he laughed. The basic experiment you are basing your work on must
be done correctly and repeatably. You are not using proper antennas,
you
have not impedance matched anything so you do not know what the fields
are, you do not have an infinite ground plane.... You probably are
seeing an odd field distribution from the geometry you have created.

My repeat of your experiment showed no anomalous effect on the phase.
In order to have any effect to discuss, you are required to show a
nonlinear phase with distance. I get a straight line for the phase
versus distance curve which means that there is a constant value for c
at all distances. It shows the same effect at different frequencies
so I also have the time dependence which thus also shows no
anomaly. There
is no point in doing the time domain experiment when you can do the
frequency domain experiment much more easily. They are equivalent and
can be done on the same piece of equipment.

One can build the modulator you suggest but there is no need. Again
the frequency domain is the same thanks to our friend fourier. I have
spent the last ten years designing and using frequency domain
radars. If
the phase versus frequency is linear at all frequencies, there is no
effect to study.




  #43  
Old April 4th 07, 05:20 PM posted to sci.physics.relativity,sci.physics,sci.physics.electromag,sci.astro
doug
external usenet poster
 
Posts: 11
Default Testing superluminal transmission of near field light waves.

I pushed the wrong button on the last post. Reply is below
William wrote:

The RF antenna group at NTNU university has looked into your network
analyzer/balanced dipole/balun experimental setup and has preformed
tests on a similar setup. They concluded that the observed phase shift
results are unreliable due to external room reflections and that the
experiment needs to be performed in an anechoic chamber.

In their tests they used an Agilent-E8364B S parameter Network Analyzer
(10MHz-50GHz), a HP 85052D4 Calibration kit, a 30cm balanced dipole
antenna with built in Balun (500MHz resonant frequency, 60cm
wavelength), an E field probe (a 0.5m cable with about 1cm exposed
wire), 1m HF Cables with SMA connectors, 10dB attenuators (placed at the
input to the Balun/Antenna and at the output of the E field probe). A
full calibration (using the cal kit - short, load, open, thru) was
performed on the analyzer including the RF cables and attached
attenuators. The Analyser was swept from 400MHz-600MHz while monitoring
the S21 phase at 500MHz. Linear as well as nonlinear phase vs distance
relations were observed as the probe was moved from next to the dipole
to the dipole wavelength (60cm).

Reflections show up quite visibly when you sweep frequencies.

A 2GHz -20GHz Anechoic chamber is available here, but preliminary tests
with the antenna at 1.5GHz (3rd harmonic of antenna) showed that phase
calibration of the analyzer is not possible due to losses in the the
long cables (10m), needed to connect the antenna and probe to the
analyzer outside the chamber.

You should use an antenna at its proper frequency.

It has been recommended that a small Anechoic chamber be constructed
specially designed for this experiment, enabling the analyzer and 1m
cables to be calibrated. The chamber should include a nonreflective
mechanism enabling the probe to be moved in small repeatable increments
within the wavelength of the antenna. The new chamber will take some
time to design, build and test, and the cost could be prohibitively
expensive. During the next few weeks I will check into this possibility.

I think they are trying to make this too hard. First of all, higher
frequencies are your friend. If possible, do the experiment at 2GHz
and put it in the anechoic chamber. I have no idea what the comment
about the long lines is about. The long lines do introduce loss and
phase shift but that is constant and, since all you want is the
slope of phase versus distance, any offset is meaningless and can be
ignored. Doing a full phase calibration is a nuisance anyway.

You can build an antenna for any frequency you want in an afternoon
in the machine shop. Small brass pipe makes a good basis. Ream it
to a convenient size to give 50 ohms with a .125" center conductor
of brazing rod, cut a slot to the length of your elements and then
make the elements out of brazing rod as well. Very careful attention
should be paid to the details of the connector end and the mating to
the connector. these antennas work very well over a +-20% bandwidth.

A much easier and cheaper way of doing this is to go outside. Mount
the antenna above the ground with its axis vertical. This puts the
minimum radiation point aimed at the ground. Put some absorber
directly below the antenna if you want. At 500MHz, the absorber is
mostly for show but if you go to 1000 or 1500MHz it actually will
absorb something. This geometry has several advantages. The
reflections are small. At higher frequencies, if you sweep enough,
you can fft the data, window out the relections and then fft back
to the frequency domain. Even without this, the reflections will
be small.



doug wrote:

William wrote:

I agree that the experiment I did should be checked, but I think it is
best to do the experiment in the lab using high frequency test equipment
like you are trying to do. As you have said the experiment is very
difficult to do right and there is a better chance of controlling all
the phenomena involved in a standard RF lab environment using commercial
test equipment. I also agree that it is essential that these
near-field measurement tests show nonlinear phase shift behavior in
the nearfield before progressing to a wide bandwidth signal
transmission experiments.

I am very surprised by your experimental results. The transverse field
phase vs distance solution I presented in my paper is what is predicted
by Maxwell's equations (p.12, near-field dipole paper). I have
checked it both analytically and numerically (p.23-25). In addition
the solution
has also been checked by other researchers, analytically and
numerically:
http://ceta.mit.edu/pier/pier56/05.0505121.Sten.H.pdf
http://xxx.lanl.gov/abs/physics/0311061

Intuitively one can also see the nonlinear phase shift by looking at
the transverse field solution (Eq. 53). The exp[i(kr-wt)] term is a
light
speed propagating term, and the part in the brackets is a complex term
that is a function of kr. This complex term can be expressed in polar
coordinates as a phasor, where the phase will cause the over phase of
the field to deviate from kr. In the nearfield, the kr term is small
thereby making the making the term in the brackets approximately
equal to 1, corresponding to 0 deg phase difference from kr. In the
farfield the
term in the brackets becomes approximately -(kr)^2 corresponding to -180
deg phase difference from kr. In between the nearfield and the farfield
the -i(kr) term is dominant, causing the phase to be about -90 deg
there. If you will refer to the transverse Electric field phase vs kr
curve (ref. fig.12) you will see that the theoretically derived curve
agrees with these observations. Relative to a light propagating field,
the phase is 0 deg in the nearfield, approximately -90 deg in between
the nearfied and farfield, and -180 deg in the farfield.

Experimentally it is known that the E field generated by a slow moving
charge is proportional to it's position. Oscillating charges cause other
nearby charges to oscillate in unison with no observed phase difference.
In the nearfield, the B field is experimentally known to be proportional
to the current. Oscillating charges are known to generate magnetic
fields which are -90 deg phase shifted from the charge motion. In the
farfield it has been experimentally observed that the transverse
electric and magnetic fields are in phase and propagate at the speed of
light. I order for the transverse E field and B field to align in the
farfield, given that they are not aligned in the nearfield, their phase
vs distance curves must be nonlinear in the nearfield.

Do you have any ideas what the problem is? It is hard to believe that
Maxwell's equations could be wrong in the prediction of this
nonlinear phase shift effect.




The defining result is what reality thinks. After there are
reproducible experimental results, it will be the time to go through
the equations. The experiment is simple. The analysis is not and there
have been comments from others who have disagreed with your assumptions.
I am not making any assumptions about either your derivations or their
disagreements.


Until I know more exactly what you have done I can only speculate.
First of all I am extremely wary of any test that uses more than one
frequency which can generate phase shifts from band limited elements
such as the balun and antenna, or from frequency dependent
reflections. But if I understand you correctly, even though the
Analyzer is sweeping frequencies, you are effectively using only one
frequency by reading only the phase at one particular frequency as
the E field probe is moved incrementally away from the Dipole
antenna. I assume you have calibrated the Analyzer and test cables
using a calibrated short, open, and 50 ohm terminators at the end of
the test cables, thus effectively flattening out the transfer
function of these elements. I also assume the Analyzer is able to
measure at least 1 deg phase changes, which is needed to
differentiate linear from nonlinear phase behavior in the nearfield.
Can the analyzer be operated at just 1 frequency just to be sure the
sweeping is not causing any problems (eg. intermode mixing etc.).

As someone who does this kind of measurement every day, I have a pretty
good idea of the limits. First of all, the hp8753 is a stepped frequency
analyzer which sets a frequency and then takes the data so you worries
about sweeping effects do not exist. I have a stack of hp calibration
kits with a large selection of loads, mismatches, opens and shorts. The
transfer function of the system is not important at a single frequency.
It is important if you are measuring frequency dependence but that is
not being done. The data were looked at at different frequencies but
the phase comparisons were done at fixed frequencies. You can look up
the specs of the 8753 family to see what the resolutions are.

By the way have you checked that the input impedance of the
probe/Analyzer combined with the antenna to probe reactance (which
changes as the probe is moved away)is not generating a phase shift
which could be masking the true phase in the nearfield?


There are 10db attenuators at the end of the antenna and the end of
the voltage probe. This isolates the cables and test set from the
changing impedances.

Could reflections from the probe be reflecting from the Dipole
antenna causing the phase shift in the nearfield to be masked?


The probe is .5" long and this effect would show up with varying lengths
of e field probes. The two probes I used showed no difference.
I would like to make these measurements with a B field probe when I get
a chance.

In order to be able to really understand your experimental results, I
will need to know more about your experimental test setup and test
results. This will also enable the duplication of your experiment.


I am really quite surprised by these comments on things that are second
or third order effects when there are problems with your measurement
that are zeroth or first order.
You have no antenna, just a voltage probe trying to radiate.
You have no impedance match anywhere.
You have not isolated the transmitter.
You have no ground plane (the table just makes life complicated)
You have a dc circuit which does not match what you think your rf
circuit is.

The important part of the measurement is to create a geometry which is
what you think it is. A dipole antenna in free space is far more
predictable than any system with a ground plane. All parts of the
system have to be isolated from each other so you are only varying
what you think you are varyings. For instance, changing the load on
most cheap rf equipment (and the hamtronics fits that category) will
cause changes in amplitude,phase and harmonic content. Once all
the parts are properly characterized and isolated, then you can vary
whatever parameter you want with confidence that it is the only one
you are changing.

When the experiment is done properly, the results will speak for
themselves. If you get different results than I do, then we need to
look for the reason for those differences. I have listed a large
number of problems with your setup. If you fix those things, we will
be in a position to compare results.



doug wrote:

William wrote:

Hi Bill,

Thank you for the offer, but I think that duplicating the type of
experiment I showed in paper would not yield much new information.
What really needs to be done is to develop a wideband transmitter
and antenna system that can handle modulations bandwidths 1/10 of
the carrier. This will enable us to study the propagation speed of
random information, which is what everyone wants to know. This is
not a trivial design and I don't even know if it can be done. I
will have to give it some thought. If I do get something to work, I
will let you know.


trimmed discussion I am not replying to

I think you have this backwards. The first thing to do is to replicate
the experiment you did. It seems you still believe it is correct. I
have given a list of mistakes you have made. With your setup, no one
with rf experience will take it seriously. I showed it to a colleague
and he laughed. The basic experiment you are basing your work on must
be done correctly and repeatably. You are not using proper antennas,
you
have not impedance matched anything so you do not know what the fields
are, you do not have an infinite ground plane.... You probably are
seeing an odd field distribution from the geometry you have created.

My repeat of your experiment showed no anomalous effect on the phase.
In order to have any effect to discuss, you are required to show a
nonlinear phase with distance. I get a straight line for the phase
versus distance curve which means that there is a constant value for c
at all distances. It shows the same effect at different frequencies
so I also have the time dependence which thus also shows no
anomaly. There
is no point in doing the time domain experiment when you can do the
frequency domain experiment much more easily. They are equivalent and
can be done on the same piece of equipment.

One can build the modulator you suggest but there is no need. Again
the frequency domain is the same thanks to our friend fourier. I have
spent the last ten years designing and using frequency domain
radars. If
the phase versus frequency is linear at all frequencies, there is no
effect to study.




  #44  
Old April 4th 07, 06:29 PM posted to sci.physics.relativity,sci.physics,sci.physics.electromag,sci.astro
Bill Miller
external usenet poster
 
Posts: 9
Default Testing superluminal transmission of near field light waves.

Doug ...

Just one comment. I've been to Trondheim. I'm not sure if the snow has
melted enough yet for outdoor experiments! But a big gymnasium might work!

Otherwise, your suggestions are spot on.

Bill Miller
"doug" doug@doug wrote in message
...
I pushed the wrong button on the last post. Reply is below
William wrote:

The RF antenna group at NTNU university has looked into your network
analyzer/balanced dipole/balun experimental setup and has preformed tests
on a similar setup. They concluded that the observed phase shift results
are unreliable due to external room reflections and that the experiment
needs to be performed in an anechoic chamber.

In their tests they used an Agilent-E8364B S parameter Network Analyzer
(10MHz-50GHz), a HP 85052D4 Calibration kit, a 30cm balanced dipole
antenna with built in Balun (500MHz resonant frequency, 60cm wavelength),
an E field probe (a 0.5m cable with about 1cm exposed wire), 1m HF Cables
with SMA connectors, 10dB attenuators (placed at the input to the
Balun/Antenna and at the output of the E field probe). A full calibration
(using the cal kit - short, load, open, thru) was performed on the
analyzer including the RF cables and attached attenuators. The Analyser
was swept from 400MHz-600MHz while monitoring the S21 phase at 500MHz.
Linear as well as nonlinear phase vs distance relations were observed as
the probe was moved from next to the dipole to the dipole wavelength
(60cm).

Reflections show up quite visibly when you sweep frequencies.

A 2GHz -20GHz Anechoic chamber is available here, but preliminary tests
with the antenna at 1.5GHz (3rd harmonic of antenna) showed that phase
calibration of the analyzer is not possible due to losses in the the long
cables (10m), needed to connect the antenna and probe to the analyzer
outside the chamber.

You should use an antenna at its proper frequency.

It has been recommended that a small Anechoic chamber be constructed
specially designed for this experiment, enabling the analyzer and 1m
cables to be calibrated. The chamber should include a nonreflective
mechanism enabling the probe to be moved in small repeatable increments
within the wavelength of the antenna. The new chamber will take some time
to design, build and test, and the cost could be prohibitively expensive.
During the next few weeks I will check into this possibility.

I think they are trying to make this too hard. First of all, higher
frequencies are your friend. If possible, do the experiment at 2GHz
and put it in the anechoic chamber. I have no idea what the comment
about the long lines is about. The long lines do introduce loss and
phase shift but that is constant and, since all you want is the
slope of phase versus distance, any offset is meaningless and can be
ignored. Doing a full phase calibration is a nuisance anyway.

You can build an antenna for any frequency you want in an afternoon
in the machine shop. Small brass pipe makes a good basis. Ream it
to a convenient size to give 50 ohms with a .125" center conductor
of brazing rod, cut a slot to the length of your elements and then
make the elements out of brazing rod as well. Very careful attention
should be paid to the details of the connector end and the mating to
the connector. these antennas work very well over a +-20% bandwidth.

A much easier and cheaper way of doing this is to go outside. Mount
the antenna above the ground with its axis vertical. This puts the
minimum radiation point aimed at the ground. Put some absorber
directly below the antenna if you want. At 500MHz, the absorber is
mostly for show but if you go to 1000 or 1500MHz it actually will
absorb something. This geometry has several advantages. The
reflections are small. At higher frequencies, if you sweep enough,
you can fft the data, window out the relections and then fft back
to the frequency domain. Even without this, the reflections will
be small.



doug wrote:

William wrote:

I agree that the experiment I did should be checked, but I think it is
best to do the experiment in the lab using high frequency test
equipment
like you are trying to do. As you have said the experiment is very
difficult to do right and there is a better chance of controlling all
the phenomena involved in a standard RF lab environment using
commercial
test equipment. I also agree that it is essential that these near-field
measurement tests show nonlinear phase shift behavior in the nearfield
before progressing to a wide bandwidth signal transmission experiments.

I am very surprised by your experimental results. The transverse field
phase vs distance solution I presented in my paper is what is predicted
by Maxwell's equations (p.12, near-field dipole paper). I have checked
it both analytically and numerically (p.23-25). In addition the
solution
has also been checked by other researchers, analytically and
numerically:
http://ceta.mit.edu/pier/pier56/05.0505121.Sten.H.pdf
http://xxx.lanl.gov/abs/physics/0311061

Intuitively one can also see the nonlinear phase shift by looking at
the transverse field solution (Eq. 53). The exp[i(kr-wt)] term is a
light
speed propagating term, and the part in the brackets is a complex term
that is a function of kr. This complex term can be expressed in polar
coordinates as a phasor, where the phase will cause the over phase of
the field to deviate from kr. In the nearfield, the kr term is small
thereby making the making the term in the brackets approximately equal
to 1, corresponding to 0 deg phase difference from kr. In the farfield
the
term in the brackets becomes approximately -(kr)^2 corresponding
to -180
deg phase difference from kr. In between the nearfield and the farfield
the -i(kr) term is dominant, causing the phase to be about -90 deg
there. If you will refer to the transverse Electric field phase vs kr
curve (ref. fig.12) you will see that the theoretically derived curve
agrees with these observations. Relative to a light propagating field,
the phase is 0 deg in the nearfield, approximately -90 deg in between
the nearfied and farfield, and -180 deg in the farfield.

Experimentally it is known that the E field generated by a slow moving
charge is proportional to it's position. Oscillating charges cause
other
nearby charges to oscillate in unison with no observed phase
difference.
In the nearfield, the B field is experimentally known to be
proportional
to the current. Oscillating charges are known to generate magnetic
fields which are -90 deg phase shifted from the charge motion. In the
farfield it has been experimentally observed that the transverse
electric and magnetic fields are in phase and propagate at the speed of
light. I order for the transverse E field and B field to align in the
farfield, given that they are not aligned in the nearfield, their phase
vs distance curves must be nonlinear in the nearfield.

Do you have any ideas what the problem is? It is hard to believe that
Maxwell's equations could be wrong in the prediction of this nonlinear
phase shift effect.



The defining result is what reality thinks. After there are
reproducible experimental results, it will be the time to go through
the equations. The experiment is simple. The analysis is not and there
have been comments from others who have disagreed with your assumptions.
I am not making any assumptions about either your derivations or their
disagreements.


Until I know more exactly what you have done I can only speculate.
First of all I am extremely wary of any test that uses more than one
frequency which can generate phase shifts from band limited elements
such as the balun and antenna, or from frequency dependent reflections.
But if I understand you correctly, even though the Analyzer is sweeping
frequencies, you are effectively using only one frequency by reading
only the phase at one particular frequency as the E field probe is
moved incrementally away from the Dipole antenna. I assume you have
calibrated the Analyzer and test cables using a calibrated short, open,
and 50 ohm terminators at the end of the test cables, thus effectively
flattening out the transfer function of these elements. I also assume
the Analyzer is able to measure at least 1 deg phase changes, which is
needed to differentiate linear from nonlinear phase behavior in the
nearfield. Can the analyzer be operated at just 1 frequency just to be
sure the sweeping is not causing any problems (eg. intermode mixing
etc.).

As someone who does this kind of measurement every day, I have a pretty
good idea of the limits. First of all, the hp8753 is a stepped frequency
analyzer which sets a frequency and then takes the data so you worries
about sweeping effects do not exist. I have a stack of hp calibration
kits with a large selection of loads, mismatches, opens and shorts. The
transfer function of the system is not important at a single frequency.
It is important if you are measuring frequency dependence but that is
not being done. The data were looked at at different frequencies but
the phase comparisons were done at fixed frequencies. You can look up
the specs of the 8753 family to see what the resolutions are.

By the way have you checked that the input impedance of the
probe/Analyzer combined with the antenna to probe reactance (which
changes as the probe is moved away)is not generating a phase shift
which could be masking the true phase in the nearfield?


There are 10db attenuators at the end of the antenna and the end of
the voltage probe. This isolates the cables and test set from the
changing impedances.

Could reflections from the probe be reflecting from the Dipole antenna
causing the phase shift in the nearfield to be masked?


The probe is .5" long and this effect would show up with varying lengths
of e field probes. The two probes I used showed no difference.
I would like to make these measurements with a B field probe when I get
a chance.

In order to be able to really understand your experimental results, I
will need to know more about your experimental test setup and test
results. This will also enable the duplication of your experiment.


I am really quite surprised by these comments on things that are second
or third order effects when there are problems with your measurement
that are zeroth or first order.
You have no antenna, just a voltage probe trying to radiate.
You have no impedance match anywhere.
You have not isolated the transmitter.
You have no ground plane (the table just makes life complicated)
You have a dc circuit which does not match what you think your rf
circuit is.

The important part of the measurement is to create a geometry which is
what you think it is. A dipole antenna in free space is far more
predictable than any system with a ground plane. All parts of the
system have to be isolated from each other so you are only varying
what you think you are varyings. For instance, changing the load on
most cheap rf equipment (and the hamtronics fits that category) will
cause changes in amplitude,phase and harmonic content. Once all
the parts are properly characterized and isolated, then you can vary
whatever parameter you want with confidence that it is the only one
you are changing.

When the experiment is done properly, the results will speak for
themselves. If you get different results than I do, then we need to
look for the reason for those differences. I have listed a large
number of problems with your setup. If you fix those things, we will
be in a position to compare results.



doug wrote:

William wrote:

Hi Bill,

Thank you for the offer, but I think that duplicating the type of
experiment I showed in paper would not yield much new information.
What really needs to be done is to develop a wideband transmitter and
antenna system that can handle modulations bandwidths 1/10 of the
carrier. This will enable us to study the propagation speed of random
information, which is what everyone wants to know. This is not a
trivial design and I don't even know if it can be done. I will have
to give it some thought. If I do get something to work, I will let
you know.


trimmed discussion I am not replying to

I think you have this backwards. The first thing to do is to
replicate
the experiment you did. It seems you still believe it is correct. I
have given a list of mistakes you have made. With your setup, no one
with rf experience will take it seriously. I showed it to a colleague
and he laughed. The basic experiment you are basing your work on must
be done correctly and repeatably. You are not using proper antennas,
you
have not impedance matched anything so you do not know what the fields
are, you do not have an infinite ground plane.... You probably are
seeing an odd field distribution from the geometry you have created.

My repeat of your experiment showed no anomalous effect on the phase.
In order to have any effect to discuss, you are required to show a
nonlinear phase with distance. I get a straight line for the phase
versus distance curve which means that there is a constant value for c
at all distances. It shows the same effect at different frequencies so
I also have the time dependence which thus also shows no anomaly.
There
is no point in doing the time domain experiment when you can do the
frequency domain experiment much more easily. They are equivalent and
can be done on the same piece of equipment.

One can build the modulator you suggest but there is no need. Again
the frequency domain is the same thanks to our friend fourier. I have
spent the last ten years designing and using frequency domain radars.
If
the phase versus frequency is linear at all frequencies, there is no
effect to study.






 




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