Homebrew Microwave Interferometer
MarkTh...@hotmail.com
non contact acoustic vibration sensor? For example: if the transmitted
beam from such a system were aimed at an acoustic target playing music
(stereo) a few feet away and the reflected beam is combined with a
sample of that beam that was sent straight into the mixer, could the
acoustic micro displacements in the i.f. be phase demodulated so that
the audio could be heard and understood?
How could this be done exactly? Could an audio amp be connected
straight onto the radars mixer pin and reproduce the audio, or would
it require that the phase information be detected in an audio version
of a pll and then amplified? What components would be needed exactly
to connect to the radars microwave mixer pin to acheive this?
I am curious if microwaves can be utilized like lasers can such as
used in the laser listener systems that are well known. There is
unending amounts of information on the laser systems, but none on the
microwave versions. Tia.
Rene Tschaggelar
The surface just has to reflect the microwaves to a sufficient degree.
A homodyne detection as in the interferometer has the phase as output.
And since this phase corresponds to the amplitude, you could basically
connect an amp there.
Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net
Arthur Jernberg
applications and demands.
"Rene Tschaggelar" <tscha...@dplanet.ch> wrote in message
news:3DE604C0...@dplanet.ch...
John Jardine
markth...@Hotmail.com <MarkTh...@Hotmail.com> wrote in message
news:b82f9928.02112...@posting.google.com...
A 10Ghz 'direct conversion' radar mixer like used on say, the burglar alarm
detectors is pushing out 3 centimetre radiation.
A surface vibrating at an audio frequency would (I imagine) be moving to and
fro in the region of a few microns.
I'd think that the resulting audio FM at the mixer output (including
reflection and path losses) would be too low to usefully recover.
Rene Tschaggelar
There was this case where after a certain period of time some embassy
employees became suspicious of the window cleaners. They came a bit too
often. They in fact did have a salty solution that was said to be radar
reflective. I forgot the where and when of this story.
Marc H.Popek
Marc H.Popek
A) modulate the carrier to chop the audio up to higher frequency
B) recover the phase, using a low sideband noise oscillator
c) demodulate the phase carrier to extract the 1/1000 p1/2 phase modulation
that you can expect to see with a 1 uM vibration.
Marc
"John Jardine" <jo...@jjdesigns.fsnet.co.uk> wrote in message
news:as58pi$l13$1...@news6.svr.pol.co.uk...
John Woodgate
<jo...@jjdesigns.fsnet.co.uk> wrote (in <as58pi$l13$1...@news6.svr.pol.co.uk
>) about 'Homebrew Microwave Interferometer', on Thu, 28 Nov 2002:
>A 10Ghz 'direct conversion' radar mixer like used on say, the burglar alarm
>detectors is pushing out 3 centimetre radiation.
>A surface vibrating at an audio frequency would (I imagine) be moving to and
>fro in the region of a few microns.
>I'd think that the resulting audio FM at the mixer output (including
>reflection and path losses) would be too low to usefully recover.
A loudspeaker gives a nominally flat frequency response when driven with
a constant voltage. This produces a nominally constant back e.m.f., like
a motor (assuming voice-coil inductance is negligible). A constant back
e.m.f is produced by a constant cone velocity, so the amplitude is
inversely proportional to frequency. If we assume a fairly modest
excursion of 1 mm at 100 Hz, we get 10 microns at 10 kHz. That gives a
deviation of 10 GHz x (10 u)/30 = 3333 Hz.
It does not appear impracticable. But what is measured is the *average*
displacement of the whole cone, which is not all that useful I think,
whereas a laser can scan the surface and show break-up patterns.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!
John Larkin
(markth...@Hotmail.com) wrote:
Try a google search for 'gunnplexer'; that is close to what you're
proposing. There are also lots of surplus, very cheap, microwave
doppler security sensors around.
John
John Jardine
> > markth...@Hotmail.com <MarkTh...@Hotmail.com> wrote in message
> > news:b82f9928.02112...@posting.google.com...
>
> employees became suspicious of the window cleaners. They came a bit too
> often. They in fact did have a salty solution that was said to be radar
> reflective. I forgot the where and when of this story.
>
> Rene
> --
> Ing.Buero R.Tschaggelar - http://www.ibrtses.com
> & commercial newsgroups - http://www.talkto.net
I love the story of the Russians presenting a magnificent carved eagle
statue to the US Embassy in Moscow (cold war era). Ended up in one of the
conference rooms where it remained for a number of years.
Eventually discovered to contain within its base a passive resonant cavity
(appears simply as a space) that could be excited into re-radiation by an
external source of microwaves. Conversations within the room acoustically
coupled through a diaphragm into the cavity and then retransmitted out of
the building at microwave frequencies, to be listened to by nearby gentlemen
with suitable detection equipment.
To get a useable S/N Required dosing the area where the statue was with
quite high levels of RF.
After the statue was discovered. The Russians then tried to make use of
*any* fortuitive passive resonant cavity that may have existed throughout
the whole buildings structure.
This required *massive* amount of RF to be dumped on the building and led to
a number of staff falling ill to radiation sickness related problems.
Needed a diplomatic incident before the practice was ended.
regards
john
John Larkin
<j...@jmwa.demon.contraspam.yuk> wrote:
>I read in sci.electronics.design that John Jardine
><jo...@jjdesigns.fsnet.co.uk> wrote (in <as58pi$l13$1...@news6.svr.pol.co.uk
>>) about 'Homebrew Microwave Interferometer', on Thu, 28 Nov 2002:
>
>>A 10Ghz 'direct conversion' radar mixer like used on say, the burglar alarm
>>detectors is pushing out 3 centimetre radiation.
>>A surface vibrating at an audio frequency would (I imagine) be moving to and
>>fro in the region of a few microns.
>>I'd think that the resulting audio FM at the mixer output (including
>>reflection and path losses) would be too low to usefully recover.
>
>A loudspeaker gives a nominally flat frequency response when driven with
>a constant voltage. This produces a nominally constant back e.m.f., like
>a motor (assuming voice-coil inductance is negligible). A constant back
>e.m.f is produced by a constant cone velocity, so the amplitude is
>inversely proportional to frequency. If we assume a fairly modest
>excursion of 1 mm at 100 Hz, we get 10 microns at 10 kHz. That gives a
>deviation of 10 GHz x (10 u)/30 = 3333 Hz.
>
>It does not appear impracticable. But what is measured is the *average*
>displacement of the whole cone, which is not all that useful I think,
>whereas a laser can scan the surface and show break-up patterns.
Police speed guns are generally calibrated using a tuning fork.
John
MarkTh...@hotmail.com
With a flat tone...at what frequency? Could an up-converter be used on
the mixer pin instead to simplify things? No? How about utilizing a
microwave frequency that the human voice box is generally resonant at?
What is the resonant frequency of water? Maybe a microwave beam that
takes advantage of the fact that the human body is composed of a high
percentage of water.
When a person speaks the water in their body has to be modulated much
better than a window....if the beam was just slightly above or below
the human bodies water/voice box resonant frequencies, would speech
cause enough vibrations to impose on the nearby carrier strongly
enough for decent demodulation levels? A method like this, it would
seem, might cause a person to sound monotone...like a robot, or like a
person with an artificial voice box because of a health problem. What
frequency would reflect off of speech modulated air?
The carrier it would seem would have to be near this resonance instead
of on it because if it was on it it would wipe out the micro
displacements by creating its own. Am I correct about any of this?
Please forgive my ignorance.
Anyway, I think that bouncing microwaves of the proper frequencies off
of people directly instead of windows or walls would stand a better
chance of working. Just my humble opinions.
"Marc H.Popek" <LVM...@worldnet.att.net> wrote in message news:<qmsF9.35405$hK4.3...@bgtnsc05-news.ops.worldnet.att.net>...