Author Topic: Weird RF module  (Read 1028 times)

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Offline EggertEnjoyer123Topic starter

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Weird RF module
« on: May 12, 2024, 10:02:49 am »
I bought this weird RF module for a couple dollars at a ham radio. (It is a MHL70031 from Anritsu).
The device has 3 3.5mm connectors, and 24 feedthroughs. I opened up the device and took pictures using a microscope.

It appears to be some sort of amplifier. Any idea on what the module is supposed to do? My uneducated guess is that it is some sort of comparator (since all the transistors seem to be in pairs, and at the input we seem to have a differential pair with one of the transistors connected to a voltage divider).
« Last Edit: May 12, 2024, 10:04:56 am by EggertEnjoyer123 »
 
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Offline D Straney

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Re: Weird RF module
« Reply #1 on: May 12, 2024, 07:01:20 pm »
That is an absolutely wild mess of wirebonds from the DC pins.  Interesting that it has 3 coax connections.  I'd bet you could trace the full circuit if you wanted to since it's all visible there (if you can figure out the pinouts of the bare dies, that is).  A high-speed "square-ifier" that turns an RF input into two complementary fixed-amplitude outputs sounds plausible as something that could be useful in certain test equipment.

Also: wonder what's up with the two traces at the left edge that look like they're doing a narrow-to-wide transition for a coax connector, and then go nowhere?  And the weird bridge over the right-hand coax connection, that has a resistor sitting on top of it?
« Last Edit: May 12, 2024, 07:04:11 pm by D Straney »
 

Offline EggertEnjoyer123Topic starter

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Re: Weird RF module
« Reply #2 on: May 12, 2024, 08:36:27 pm »
Also: wonder what's up with the two traces at the left edge that look like they're doing a narrow-to-wide transition for a coax connector, and then go nowhere?  And the weird bridge over the right-hand coax connection, that has a resistor sitting on top of it?

The narrow to wide transitions are connected to the coax connectors. There's two coax connectors on the left and one on the right. The bridge thing contains an inductor for (presumably) DC biasing.

I'm unsure what the transistors are, since I'm not well versed in wirebond components. Look like dual gate FETs?
 

Offline D Straney

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Re: Weird RF module
« Reply #3 on: May 13, 2024, 04:48:56 pm »
The narrow to wide transitions are connected to the coax connectors. There's two coax connectors on the left and one on the right.

I was thinking of the middle two actually (see photo).

Dual-gate FET sounds plenty plausible, or dual FET on a single die.  I couldn't find any die shots of dual-gate RF FETs, but Zeptobars has a few RF BJTs, which all have interleaved-finger structures that these ones don't have:
https://zeptobars.com/en/read/Infineon-BFR740-42GHz-BJT-npn
https://zeptobars.com/en/read/BFR93-bjt-bipolar-RF-npn-transistor
https://zeptobars.com/en/read/Infineon-BFP450-linear-low-noise-BJT-Siemens-RF-24Ghz-fT
https://zeptobars.com/en/read/Infineon-BFP540FESD-30Ghz-fT-NPN-BJT-RF


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