Jason,
These gunplexer from Macom have been used for a long time to make doppler r=
adars.
Even know that they were originally intended to be use for door openers, so=
me companies
in the police radar business used them as the base device in their radar gu=
ns.

I hope that you took serious care of avoiding ESD because these devices are=
 VERY sensitive.
Not the gunn diode, but the two schotky that are the receiver part.

It is a self mixer, when you power the gunn diode, some of the transmit sig=
nal is used as the
LO for the receiver, so you get only the frequency difference (doppler)

Then you can use a DSP processor to calculate the speed.

I hope you did not turn the screw as you might have already killed the rece=
ive diodes.
There are two of them that provide I/Q signal

My $0.02,
Jean-Paul
N1JPL

I worked in one of those police radar companies a long while ago.=20





> On Apr 16, 2016, at 2:34 PM, Jason White <whitewaterssoftwareinfo@gmail.c=
om> wrote:
>=20
> Hello, Recently I saw a video demonstrating how Gunnplexers are used in
> "Radar Guns" (speed measuring). I bought a 24Ghz gunplexer [1] so that I
> could make my own radar gun. Now that I have see one up close I have some
> questions about how they work and what some of the tuning screws do. I ha=
ve
> attached a photograph to make things easier to explain.
>=20
> [Question 1]: There are two tuning screws a large brass one and a small
> silver one. What is the function of the silver tuning scew?
>=20
> The brass one is labeled as the frequency adjust screw, presumably it
> sticks down into some sort of cavity resonator. The second screw, the
> silver one, goes through the case and comes out directly in front of a
> small aperture (hole) coupling the oscillator's output into the waveguide=
..
> Right next to this screw is the mixer diode for the Doppler output. The
> screw came adjusted so that it is even with the lower edge of the
> oscillator aperture. Could this screw have something to do with the amoun=
t
> of coupling between the oscillator's output and the mixer diode?
>=20
> [Question 2]: The oscillator is coupled to the waveguide through a ~1.5mm
> eliptical hole that is much smaller that the wavelength for 24Ghz (12mm).
> How can the 24GHz from the oscillator pass through such a small hole?
>=20
> Thanks,
> Jason White
>=20
>=20
> [1] M/A-COM: MACS-007801-0M1R10 "24.125 GHz Mono Doppler Transceiver"
> Datasheet: http://cdn.macom.com/datasheets/MACS-007801-0M1R10.pdf
>=20
> --=20
> Jason White
> <180.jpg>--=20
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> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist


--=20
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