Re: time reversal wave

Bill Perry ( (no email) )
Sat, 8 Jan 2000 18:44:12 -1000

This doesn't refer to anything temporal. It is called a time-reversal wave
because it is out of phase with the incident phase. I recall someone
recommended you read the SA article about it. it was shorter, but slightly
more informative than the poptronix article, IMHO. For starters, imagine a
bunch of steel rods about 1-foot in height. We'll use 100 of them in a 10 x
10 fashion.if you put a transcucer on one side of the array, and transmit an
ultrasonic pulse into the array, the signal will get bounced around,
reflected, and refracted, resulting in a bunch of different freqs coming out
of the array from every point. So, by following this logic, the metal rod
array can be likened to a complex mathematicala function dependent primarily
on time and signal frequency.
on the other side of the array, we have about 1000 or so, ultrasonic
transducers, which receive the multitude of signals exiting the array, and
record them all in a digital memory bank. after the signal activity stops,
all the recorded signals are played BACK OUT the transducers in REVERSE
order, which is the same as plugging the answers from a math equation back
into it, to get the original starting variable(s).
so what happens, is the original ultrasonic pulse converges back on the
transducer.
Hope this view helps.
BillP
----- Original Message -----
From: DRA <orbital@rf.net>
To: <Interact@keelynet.com>
Sent: Friday, January 07, 2000 8:02 AM
Subject: time reversal wave

> In the premier issue of Poptronix (P.E. + E.N.), There is an
> interesting article claiming that a wave reflected off a phase
> conjugated mirror (PCM) effictivly generates a time reversal wave...
> now, how can a mirror vibrating, in phase, at 2x the source wave
> reverse time? does that imply that shifting the phase and/or frequincy
> could cause a time advancement wave? or better yet, a time stopping
> wave?
>
> It seems to me that time is ultimately a constant, and any precived
> shift is due to a change in the surounding frequencies. i.e. an
> airplane traveling faster than ... is being bombarded with
> particles/waves that, and due to the dopler (sp?) effect, causes an
> increase in the molecular resonance of the airplane and its contents;
> including say.. a cesium clock tht would appear to have advanced in time
> compared to one that was on the ground.
>
> can anyone recomend a detector circut capible of generating a phase
> locked loop with the earth's 7.xHz or 11.xHz resonance that i could send
> through a frequincy doubler, amplify it, and finally pass it through a
> PCM type transducer? I guess the hard part would be impedance matching
> the system.
>
>
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