David Gravereaux
October 31st 09, 09:47 PM
Hi All,
So a long time back I read it was possible to use RADAR to read
displacement from an article in AudioExpress and a posting I saw once
somewhere. So I tried myself using a cheap Mattel's Hot Wheels Radar Gun.
So I pulled the antenna out of the thing, powered it with 5V, and
watched on my o'scope. The damn thing worked, but had some issues.
10.525GHz has a wavelength of ~29mm. Doppler RADAR works on the
principal of new beat frequencies created by a reflecting object as it
passes through the wavelength boundary. These new beat frequencies are
used to calculate velocity.
In contrast with a driver who's displacement doesn't cross a wavelength
boundary -- 12mm Xmax = 24mm peak-to-peak displacement -- we are given a
phase output of the combined sent and reflected signal. This phase
output is directly displacement without a needed velocity conversion by
D = V/pi*F. It works with no fuss.
So I made a limiter using it just as fun project which I might follow
through with toward a rack-mount item for my sound system.
http://www.facebook.com/v/1234283770983
--
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (GNU/Linux)
iEYEARECAAYFAkrssHEACgkQlZadkQh/RmHiJgCffzW/0Fx8dwK2rNECgfZqJj3D
kZkAnjTY+S1GLU8luvJq1vLH0dihd2HX
=Qc+l
-----END PGP SIGNATURE-----
So a long time back I read it was possible to use RADAR to read
displacement from an article in AudioExpress and a posting I saw once
somewhere. So I tried myself using a cheap Mattel's Hot Wheels Radar Gun.
So I pulled the antenna out of the thing, powered it with 5V, and
watched on my o'scope. The damn thing worked, but had some issues.
10.525GHz has a wavelength of ~29mm. Doppler RADAR works on the
principal of new beat frequencies created by a reflecting object as it
passes through the wavelength boundary. These new beat frequencies are
used to calculate velocity.
In contrast with a driver who's displacement doesn't cross a wavelength
boundary -- 12mm Xmax = 24mm peak-to-peak displacement -- we are given a
phase output of the combined sent and reflected signal. This phase
output is directly displacement without a needed velocity conversion by
D = V/pi*F. It works with no fuss.
So I made a limiter using it just as fun project which I might follow
through with toward a rack-mount item for my sound system.
http://www.facebook.com/v/1234283770983
--
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (GNU/Linux)
iEYEARECAAYFAkrssHEACgkQlZadkQh/RmHiJgCffzW/0Fx8dwK2rNECgfZqJj3D
kZkAnjTY+S1GLU8luvJq1vLH0dihd2HX
=Qc+l
-----END PGP SIGNATURE-----