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From: "John Jardine"
Subject: Re: Homebrew Microwave Interferometer
Date: Thu, 28 Nov 2002 14:33:30 -0000
NNTP-Posting-Date: 28 Nov 2002 14:21:38 GMT
X-Newsreader: Microsoft Outlook Express 5.00.2615.200
markthomas77@Hotmail.com wrote in message
> I am curious if a 10 mw cw x-band microwave radar could be used as a
> 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.
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.
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