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posted by janrinok on Saturday July 06, @01:58PM   Printer-friendly

https://www.allaboutcircuits.com/news/teardown-tuesday-hb100-doppler-radar-module/

Join us as we crack open an HB100 Doppler radar module and delve into the mysteries of RF component design.

In this special edition of Teardown Tuesday, we crack open an HB100 Doppler radar module and delve into the mysteries of RF component design.

The HB100 Doppler Radar module costs about $5 from the usual online suspects, which is down at the "insanely cheap" end of the spectrum when you're talking about 10Ghz radio gear. Does it work? Surprisingly, yes. It needs some support components for most uses (like a post-amplifier for the "couple of millivolts" signal it outputs) but does its part of the job well enough.

[...] Frankly, I was rather shocked by what I found. I wasn't expecting much, but I got far less.

I don't know who designed this, but they were a master of the black art of Radio Frequency waveguide engineering. I am impressed. The PCB, itself, is a major component. Not only for the patch antennas but also several RF filters, the local oscillator, and the mixer are all largely made from peculiarly-shaped PCB tracks.

What would you build with it?


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  • (Score: 0) by Anonymous Coward on Saturday July 06, @02:03PM (5 children)

    by Anonymous Coward on Saturday July 06, @02:03PM (#1363292)

    Tuesday? I though it was Saturday. Man the days just fly by during the summer ...

    • (Score: 3, Funny) by janrinok on Saturday July 06, @03:09PM (3 children)

      by janrinok (52) Subscriber Badge on Saturday July 06, @03:09PM (#1363295) Journal

      It is certainly quiet without most of the USians who I suppose are eating, drinking and some will be blowing their hands off.....

      --
      I am not interested in knowing who people are or where they live. My interest starts and stops at our servers.
      • (Score: 3, Funny) by Barenflimski on Saturday July 06, @03:38PM (2 children)

        by Barenflimski (6836) on Saturday July 06, @03:38PM (#1363298)

        I blew off both of my hands and accidentally killed the neighbors dog. M80's 4 l1fe!

        • (Score: 2, Funny) by Anonymous Coward on Saturday July 06, @03:44PM (1 child)

          by Anonymous Coward on Saturday July 06, @03:44PM (#1363299)

          I blew off both of my hands and accidentally killed the neighbors dog. M80's 4 l1fe!

          So are you a hunt and pecker typist now?

    • (Score: 2) by driverless on Sunday July 07, @06:51AM

      by driverless (4770) on Sunday July 07, @06:51AM (#1363363)

      Bound to be Tuesday somewhere...

  • (Score: 4, Informative) by RS3 on Saturday July 06, @02:44PM (7 children)

    by RS3 (6367) on Saturday July 06, @02:44PM (#1363293)

    I'm pretty sure the one thing with a hat (disc on top) is a circulator [wikipedia.org]. I've not yet seen them in that package, but the thing on top makes me think it could be a magnet, which would cause signal circulation. The pics aren't super clear, but it looks like a circular arrow printed on the top.

    Anyone else recognize it?

    • (Score: 2) by janrinok on Saturday July 06, @03:11PM (5 children)

      by janrinok (52) Subscriber Badge on Saturday July 06, @03:11PM (#1363296) Journal

      That would better explain how it works - thanks for that info. It is not a component that I have knowingly used.

      --
      I am not interested in knowing who people are or where they live. My interest starts and stops at our servers.
      • (Score: 2) by RS3 on Saturday July 06, @05:00PM (4 children)

        by RS3 (6367) on Saturday July 06, @05:00PM (#1363304)

        You're most welcome. As I did a bit more searching, I'm not so sure that part is a pure circulator- it may be a semiconductor with a wave-steering magnet on top. If so, it's a pretty interesting way to do semiconductor physics. If not, maybe I just invented something (very doubtful).

        Not the same thing, but you might also think about a magnetron [wikipedia.org], or "cavity magnetron" tube (valve? :) which uses a magnet to steer electrons.

        • (Score: 2) by janrinok on Saturday July 06, @05:18PM (3 children)

          by janrinok (52) Subscriber Badge on Saturday July 06, @05:18PM (#1363307) Journal

          Magnetrons I know. I have yet to see one that small and using such a minute amount of power (at least for a magnetron) so I am doubtful that this is what it is. However, my knowledge of them is now getting dated so perhaps there is something new that I have missed.

          --
          I am not interested in knowing who people are or where they live. My interest starts and stops at our servers.
          • (Score: 2) by RS3 on Saturday July 06, @05:29PM (2 children)

            by RS3 (6367) on Saturday July 06, @05:29PM (#1363308)

            I'm sorry, you completely misunderstood me. I was not trying to say the microwave circuit had a magnetron; I was just drawing a comparison to another electronic component where a magnet is used to steer electrons.

            • (Score: 2) by janrinok on Saturday July 06, @05:42PM (1 child)

              by janrinok (52) Subscriber Badge on Saturday July 06, @05:42PM (#1363310) Journal

              OK, I am still wondering what the component actually is. Your suggestion a couple of comments back seemed to fit the bill perfectly.

              --
              I am not interested in knowing who people are or where they live. My interest starts and stops at our servers.
              • (Score: 3, Interesting) by RS3 on Saturday July 06, @06:14PM

                by RS3 (6367) on Saturday July 06, @06:14PM (#1363311)

                I'm guessing it's a circulator. If you click the first link I provided it'll tell you what a circulator is, how it works, what it's used for, etc.

                But, doing a web search on circulator images, I don't see any that look like the part on the board.

                Also, I didn't study the circuit in detail, but it seems that the part needs to be an active (transistor) part, not not a passive.

                So, it might be a transistor with a magnet glued on.

                Again, it'll all become clear if you take a look at the circulator wiki.

    • (Score: 3, Informative) by RS3 on Saturday July 06, @10:20PM

      by RS3 (6367) on Saturday July 06, @10:20PM (#1363341)

      Correction: that part is most likely a power GaAs-FET (gallium-arsenide field-effect transistor). That circular "hat" had me fooled into thinking it was a magnet like on a circulator. Further research reveals that there are GaAs FETs that look exactly like that. So I doubt it's a magnet- just an interesting SMD package style.

      Also, circulators are often used in RADAR circuits: they allow you to use one antenna for both transmit and receive. Yes, the spooky world of microwave stuff.

  • (Score: 4, Interesting) by VLM on Saturday July 06, @04:00PM (1 child)

    by VLM (445) on Saturday July 06, @04:00PM (#1363300)

    For more DRO fun you can check out direct broadcast satellite LNBs that are essentially free at rummage sales and thrift stores (for DirectTV and similar). They are not frequency stable enough for narrowband stuff but are "stable enough" for digital TV satellite service or screwing around with ham radio stuff. An interesting, weird, cool, tech.

    The article author seemed confused about YIG technology when he was pondering if the DRO used magnets somehow. YIGs are cool but a BIT power hungry. Like watts of input to get a couple dBm of output. They are also cool tech but I don't know how you get one other than being ungodly wealthy or mil surplus. YIGs are the components that made HP 1980s microwave gear have six digit price tags. I bought a stack of them at a hamfest "decade or two ago" for pretty much nothing, thought I was wealthy, but little $20 solid state VCO modules have taken over the industry so they are indeed worth like $1 a piece now. Funny that a replacement YIG used to sell for more than a new car in the 80s, but times change fast in electronics hardware...

    • (Score: 5, Interesting) by VLM on Saturday July 06, @04:09PM

      by VLM (445) on Saturday July 06, @04:09PM (#1363301)

      so they are indeed worth like $1 a piece now.

      Correction, $1 a piece for hobbyist use, unknown condition, no serial number, etc.

      Famously there's a guy on ebay selling refurb and tested HP YIGs for a cool kilobuck a piece. Not new, but repaired. New in box, back when they were available, were like $20K and up.

      If you've ever wondered why you can get "untested" aka broken HP microwave gear from the 80s up to 90s for only $100, but guaranteed tested and working to published spec is like $1100, well, this one single component is why.

      Something in the yig wears our or breaks over time; I don't know what, thermal expansion/contraction stress, or physical shock or maybe some slow corrosion, donno? In theory a YIG should run forever, but they sure as hell do not, and are very expensive to repair, something of a miracle they're repairable at all.

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