Friday, August 19, 2011

MIT Opencourseware Site is now up: Build a Small Radar System Capable of Sensing Range, Doppler, and Synthetic Aperture Radar Imaging

A radar signal image superimposed on an overhead photo of a large steel scultpure, plus a photo of a student-built radar system.

Now you too can teach yourself how to

Build a Small Radar System Capable of Sensing Range, Doppler, and Synthetic Aperture Radar Imaging


Goto the MIT Opencourseware site for this class to view all lecture slides, read the how-to instructions on the coffee can radar kit, and see results from the doppler, ranging, and SAR imaging experiments.

Stay tuned to OCW because periodic updates to this site will include samples of data acquired from a coffee can radar and additional resources.

12 comments:

  1. Do you have a spreadsheet of the BOM available? I'm planning on building a copy and a sortable list of parts would help.

    Thanks,
    -Scott

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  2. Thank you for your comment Scott,

    Yes, the BOM is available here:
    http://ocw.mit.edu/resources/res-ll-003-build-a-small-radar-system-capable-of-sensing-range-doppler-and-synthetic-aperture-radar-imaging-january-iap-2011/projects/

    Cheers,
    Greg

    ReplyDelete
  3. Actually, I was hoping for an .xls file so I could sort the BOM to make ordering parts just a little bit easier. I ordered the Mini Circuits components yesterday. Placing orders for the rest of the parts this week.

    Any thoughts on trimming the cantennas without a network analyzer? I was thinking about making a simple 2.4 GHz SWR meter. Will just cutting the probe to the nominal length listed in the class notes be sufficient?

    Thanks,
    Scott

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  4. I ordered all the Mini Circuits parts yesterday and I'll be ordering the rest of the parts this week. Looking forward to a fun project.

    Any thoughts on trimming the cantennas without a network analyzer? Is just cutting the probes to the nominal length listed in the notes sufficient? I may try and rig up a simple SWR meter for 2.4 GHz.

    Thanks!
    -Scott

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  5. Hi Scott,

    The length of the wire probe and the exact SMA connector part number should be used in concert to provide an antenna that is already tuned up without having to check on a VNA.

    Alternatively, you could use your VCO & attenuator & driver amplifier (the output of this signal chain should be about 16 dBm) and buy a directional coupler on ebay or from mini-circuits that covers the 2.4 GHz band, then measure the reflected power with a microwave detector. You should measure 3 dBm or less on a -10 dB reverse directional coupler when the antenna is matched.

    If you come up with a better scheme then please document it and post it online. Also, i encourage you to make youtube videos of your radar in action since only a few yet exist :)

    Greg

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  6. My radar is working. Hoping to take some quantitative doppler data this weekend. Right now I've got the output hooked up to a speaker and you can hear the doppler tone as objects come and go. Thanks!

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  7. That's awesome!!! Scott, can you post online or e-mail some of your results to me?



    Greg

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  8. I will definitely post some results, but I'll be away from the project for about a week.

    Here's a question: I tried looking at my antenna match with a Mini Circuits ZX47-60 power detector and a MAC 3204-20dB bidirectional coupler, but I'm a bit baffled by the results.

    If I run the ZX95 osc through a 20 dB attenuator into the power detector, I get about -11 dBm, so the osc is producing 9 dBm (more than the typical spec of 6dBm).

    Now if I put the -11dBm (osc & 20 dB attenuator) into the coupler and place 50 ohm terminators on all the ports except the one I'm measuring power at I get funny results.

    case 1: taps have terminators, I measure -15dBm out the other side. Seems low.

    case 2: terminate the output and measure the -20 dB forward couple. -55 dBm

    case 3: terminate output and fwd couple, measure backward couple: -33 dBm.

    Is this to be expected? Shouldn't I get -31 dBm fwd and almost nothing backward?

    Perhaps I've got the ports confused? Are the side ports the taps and the tap farthest from the input is the fwd tap, the one closest to the input is the backward tap?

    Sweeping the osc freq and looking at what I think is the reflected power, I see that it's always about 3 dB less than the fwd power, but my results with the coupler alone confuse me.

    Any help would be appreciated.

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  9. Some thought after my last post and some Google confirmed that I had the taps misidentified. I'll post some plots of reflected power vs freq.

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  10. That's great news Scott! You will get there.

    If you get stuck take a few hours off and come back to it. It is surprising how many of these issues fix themselves after a 2nd look.

    Cheers,
    Greg

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  11. I've been away form the radar for a few weeks, but I'll be at MIT/LL on the 6th for an all day program review. Perhaps we can meet up for a few minutes and say hello.

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  12. Hi Scott, drop me a note so that we can settle on a time: http://web.mit.edu/bin/cgicso?query=charvat

    Be sure to bring photos, data, or any info relevant to what problems you might have at the moment. I've seen just about every problem that can be had with this radar so there is a good chance we can solve it. If possible bring the radar unit itself.

    Greg

    ReplyDelete