Anyone making a RADAR?

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rthorntn
Posts: 4
Joined: Wed Mar 06, 2013 5:16 pm

Anyone making a RADAR?

Post by rthorntn » Mon Oct 21, 2013 10:55 pm

Hi,

I thought that would be cool but I have no idea to start, on IRC there was a suggestion to post here because it had been mentioned before.

I guess I was thinking a couple of cantennas, a stepper to rotate it, 2.4Ghz freq with a 4w ebay wifi amplifier on the TX side and feeding it in to radr somehow.

Anybody got anything to share?

Thanks for looking.

Cheers
Richard

volvox_voxel
Posts: 2
Joined: Tue Jul 14, 2015 9:24 pm

Re: Anyone making a RADAR?

Post by volvox_voxel » Wed Jul 15, 2015 2:36 pm

worth a try:
I think you can make a simple working radar with a nuand.. Have you ever heard of CW radar? Using GNU radio , you can transmit a single tone, and record the I and Q signals, say within a 100KHz band around the tone you transmitted . Using inexpensive dish antennas, you could use one to transmit, and another to receive. You'd be able to detect the Doppler shift for objects moving toward or away from you depending on if ether I or Q are leading when looking at the waveforms in the time domain. You may need an amplifier on the transmitter.. CW radar will give you velocity estimates, but not range estimation. I and Q allows you to measure the magnitude and phase of the return.. The cantenna approach does not give you the sign of the doppler shift..

If you can get a single tone to work, you could make a linear chirp to give you a frequency-modulated-continuous wave radar (FMCW), to give you a range estimation. The wider the bandwidth, the better your range resolution. This is subject to the limitation of the lime-micro receiver chip and ISM band limits. This would also allow you to do matched filtering, and all kinds of other interesting tricks..

When I built a radar with RF parts, I referenced the same local oscillator for the receiver and transmitter. Does anyone know what kind of limitations there exists for listening to a tone very close to where you're transmitting? Do we see reciprocal mixing product issues (phase-noise) etc.. I'm assuming that the receiver and transmitter are coherent, as they reference the same clock, etc.

Does anyone know how fast you can ramp frequencies beyond the frequency range given to you by the internal DACs? e.g. How fast can you tune the local oscillator?

-Joe

jynik
Posts: 455
Joined: Thu Jun 06, 2013 8:15 pm

Re: Anyone making a RADAR?

Post by jynik » Wed Jul 15, 2015 6:40 pm

volvox_voxel wrote: Does anyone know how fast you can ramp frequencies beyond the frequency range given to you by the internal DACs? e.g. How fast can you tune the local oscillator?
I'm not too sure what you mean about "...how fast you can ramp frequencies beyond the frequency range..." - could you elaborate more there?

However, I think I can lead you to some info with regard to retuning times. Take a gander at the latest blog post and the frequency tuning page of the API docs. There you'll find some numbers and some advice on where you can measure a voltage used to control the LO (at the very and of the API docs page). Watching it the VTUNE pin settle out will give you a rough idea of when the tuning is complete. This will probably ultimately lead you into reviewing the LMS6002D docs and the code.

Hope that helps,
Jon

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