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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?
(Score: 2) by RS3 on Saturday July 06 2024, @05:00PM (4 children)
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 2024, @05:18PM (3 children)
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 2024, @05:29PM (2 children)
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 2024, @05:42PM (1 child)
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 2024, @06:14PM
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.