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From: Archimedes Plutonium on 4 Jun 2010 13:57


Enrico wrote:
> On Jun 4, 12:06 am, Archimedes Plutonium
> <plutonium.archime...(a)gmail.com> wrote:
> > I mentioned Wikipedia as making this mistake, so I should display what
> > I
> > deem a mistake:
> >
> > --- quoting Wikipedia ---http://en.wikipedia.org/wiki/Doppler_effect#Radar
> > Radar
> > Main article: Doppler radar
> >
> > The Doppler effect is used in some types of radar, to measure the
> > velocity of detected objects. A radar beam is fired at a moving target
> > — e.g. a motor car, as police use radar to detect speeding motorists —
> > as it approaches or recedes from the radar source. Each successive
> > radar wave has to travel farther to reach the car, before being
> > reflected and re-detected near the source. As each wave has to move
> > farther, the gap between each wave increases, increasing the
> > wavelength. In some situations, the radar beam is fired at the moving
> > car as it approaches, in which case each successive wave travels a
> > lesser distance, decreasing the wavelength. In either situation,
> > calculations from the Doppler effect accurately determine the car's
> > velocity. Moreover, the proximity fuze, developed during World War II,
> > relies upon Doppler radar to explode at the correct time, height,
> > distance, etc.[citation needed]
> > --- end quoting ---
> >
> > In short, I feel the above is pure rubbish. That radar measures speed
> > by simply two echoes
> > each giving d_1, t_1 and then d_2, t_2 and using those distances and
> > times to calculate speed.
> >
> > I feel the erroneous culture of Doppler shifted radar waves has
> > permeated the mainstream.
> >
> > I am arguing in this chapter and trying to prove that no light waves
> > are ever Doppler shifted
> > due to Special Relativity would be violated.
> >
> > Archimedes Plutoniumhttp://www.iw.net/~a_plutonium/
> > whole entire Universe is just one big atom
> > where dots of the electron-dot-cloud are galaxies
>
> ================================================================
>
> http://www.vectorsite.net/ttradar_3.html
>
> In early radars, all the radar did was display the return trace to the
> radar operator, and the radar operator had to interpret it, picking
> the target out of
>
> noise and estimating its range, direction, speed, and size.
>
> [3.5] TIME VERSUS FREQUENCY DOMAIN / PULSE DOPPLER RADARS
> * The full answer to the problem of clutter was the development of the
> "pulse Doppler" radar, hinted at in the previous chapter, which can
> obtain range data by timing radar returns, and velocity data by
> measuring the Doppler shift of the returns.
>
> > I don't like the quotes around the term: pulse Doppler. It suggests that it's actually something else.
>
> > The next sentence says it's getting velocity data by measuring the Doppler shift of the returns.
>
> > The rest of the section gets into Fields and Waves for Electrical Engineers.
>
> It is impossible to perform any sort of Doppler processing on a simple
> pulsed radar, since the Doppler frequencies will be much closer to the
> center frequency than the ends of the mainlobe band, remaining buried
> inside the mainlobe spectrum, with no way to pick them out. In other
> words, the normal variation in frequency of the signal due to its
> spectrum of components covers a continuous range that masks out any
> variations due to Doppler shifting.
>
> ...
>
> With a simple pulse radar, a low PRF / long pulse interval is useful
> to eliminate range ambiguities and ghosts. However, from the point of
> view of Doppler processing with a pulsed coherent radar, a low PRF
> means that the spectral lines are spaced closely together, making it
> very difficult to pick out Doppler frequencies in the returns. If the
> Doppler-shifted return has exactly the same frequency as one of the
> lines in the transmit spectrum, there will be no way to detect the
> "blind speed". If the Doppler-shifted return has a frequency greater
> than that of the line above the transmit line that actually produced
> it, it will give an ambiguous velocity; as will a Doppler-shifted
> return with a frequency lower than the line below.
>
> This this something of a frequency-domain "mirror" of the blind zones
> and range ambiguities discussed previously for simple pulse radars.
>
> > Yeah, it really says "This this something..."
>
> In other words, a low PRF results in little range ambiguity but
> troublesome Doppler ambiguities. A high PRF results in exactly the
> opposite situation: little Doppler ambiguity but troublesome range
> ambiguities. Of course, it is possible to get the best of both worlds
> by using a "pulse burst" scheme, with the transmitter sending out
> pulses on a long interval to get range and interleaving sets of short
> interval pulses to get velocity.
>
> ...
>
> A modern pulse Doppler radar can in principle operate in multiple
> modes. In the "low PRF" mode, the radar can obtain unambiguous ranges
> at the expense of highly ambiguous Doppler velocities. In the "high
> PRF" mode, the radar can obtain unambiguous velocities at the expense
> of highly ambiguous ranges, though FM ranging, with successive pulses
> emitted at increasing frequencies in a "ramp" pattern, can be used to
> reduce the ambiguities.
>
> > I'm not sure about that "though FM ranging, with successive pulses emitted at increasing > frequencies" part. Could the timing of the successive pulses be sneaking into the signal > processing math somewhere?
>
> Dunno. I've always assumed that doppler signal processing involved
> "beat frequencies" generated by adding the radar return signal with a
> standard. Maybe that's what effectively happens in the signal
> processing math. Maybe not. To find out for sure, I'd have to go back
> to school.
>
> I'll stick with the Moessbaur Effect gamma ray absorption experiments.
> There, detection is sharply constrained by frequency.
>
>
> Curses and Drat!
> Enrico

Thanks for writing the above Enrico, and it looks as though you were
talking to
someone else, but I cannot make out who you were talking with.

I think I solved the above. The outgoing radar is Doppler shift
modulated, but the
echoes are just as the old method of calculating. So it is not fair to
call this
a Doppler Effect Radar. It is not fair to call it a Doppler Effect
because the object desired
speed to be measured does not create a Doppler Shift on the radar. The
radar
source is modulating the sent out radar signal. To call the radar
source that is
modulated, to call it a Doppler Shift is rather unfair to the physics
definition
of Doppler Shift Effect. It should be called simply Source Modulated
Radar,
for the speeding car or the moving ship on the horizon, those speeds
were
not gathered due to a Doppler Shift on Radar. Those speeds were
gathered
due to at least two returning echoes of range and time.

The speed, range and direction of motion of the desired object is all
measured
as the old way of calculation of two separate echoes with d_2 - d_1/
t_2 - t_1

So these Doppler Radars, Enrico, are misnomered radars.

And this further supports my claim, that here on Earth, there are no
commonplace
incidents of any Doppler Shift of any form of EM waves. Only the
astronomers
with distant galaxies are claiming the existence of doppler shifted EM
waves.
This thus smells of a fake rat in physics, that no EM waves are
affected by a
Doppler Shift and none should be affected since it would violate the
Principle
of Special Relativity.


Archimedes Plutonium
http://www.iw.net/~a_plutonium/
whole entire Universe is just one big atom
where dots of the electron-dot-cloud are galaxies
From: Craig Markwardt on 4 Jun 2010 22:55
On Jun 4, 1:57 pm, Archimedes Plutonium
<plutonium.archime...(a)gmail.com> wrote:
> The speed, range and direction of motion of the desired object is all
> measured
> as the old way of calculation of two separate echoes with d_2 - d_1/
> t_2 - t_1
>
> So these Doppler Radars, Enrico, are misnomered radars.
>

Apparently he doesn't understand what "continuous wave" is.
Previous quote:
> Police traffic radar emits an unmodulated continuous wave (CW) and
> measures' reflections

CM
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