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Affordable <200MHz PDN analysis / impedance measurement hardware?

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Kean:
Thanks.  I hadn't got around to looking into it too far, and that sounds better than I expected.

Pity about the hardware side.  I bought it to complement my existing NanoVNA V2 Plus4 and LiteVNA 64, for lower frequency measurements.
I'll try run your test once it arrives.  I ordered it a week ago and it doesn't seem to have hopped on a flight yet.

ftg:
All SA602/SA612/NE602/NE612 have had the same die inside since the Philips fab making 602's burned down.

I wonder how NanoVNA pricing will go in the future, now that SA612 is out of production.
https://www.nxp.com/products/no-longer-manufactured/double-balanced-mixer-and-oscillator:SA612AD


inevitableavoidance:

--- Quote from: joeqsmith on November 19, 2024, 06:10:17 pm ---Guessing you removed the mask where L3 silkscreen is and went right to the pin.  I was a bit concern I may damage the mask and short out the supply so I elevated them a bit when I soldered them.

--- End quote ---

Right there indeed. I've recently had a colleague do some hyperlynx simulations of the difference a couple of millimeters of trace makes to the inductance (and thus high frequency impedance) of decoupling capacitors, which turns out to be more significant than the type of MLCC you'd pick. The fact that they have a 100pF capacitor in that board makes no sense (in general since a 100nF has the same parasitic inductance but also specifically) with the inductance that's still between the IC's power pins. High frequency operated ICs that have the power pins on different sides of the package make no sense to me!

In the same sense, more is simply better, as they all parallel to decrease the ESR and ESL. I'm curious what further high end improvement you'd be able to get adding more close by.

inevitableavoidance:
Scored some more dynamic range by fully soldering down the circumference of the RX Shield. Blue = unmodified, green = optimized decoupling, red = soldered down RX shield:



Didn't improve it everywhere, but it is looking 'cleaner'. Curious what the rest is caused by.

Do you have any clue what repeating pattern I'm seeing here? I've zoomed in the first bit and overlayed it with the second occurrence.

joeqsmith:

--- Quote from: inevitableavoidance on November 20, 2024, 09:25:39 am ---
--- Quote from: joeqsmith on November 19, 2024, 06:10:17 pm ---Guessing you removed the mask where L3 silkscreen is and went right to the pin.  I was a bit concern I may damage the mask and short out the supply so I elevated them a bit when I soldered them.

--- End quote ---
Right there indeed.    .... with the inductance that's still between the IC's power pins.

--- End quote ---

I did not pay attention to the layout when I pulled the mixers.  I don't know where the optimum location is.  Looks like they may have had a ground right under the part.  It may provide a shorter loop.    We are more interested in the H4's low frequency performance for PDN work.    The port matching is better on the original NanoVNAs we have and the released firmware is also more stable now.   We were using a hacked up version of firmware on the original NanoVNA to get something stable enough to use.   Although I have had the current release lockup at least twice, requiring a power cycle.  I would like to see a flavor of firmware that provides full access to the remote interface and removes any unnecessary code that is not required to run it headless (in hopes of something rock solid), and change the protocol to match the LiteVNA...   

Beyond narrow band measurements and the improved low frequency performance the H4 offers, I use the LiteVNA. 

***
I am sure they have switch points in the firmware.  Plus harmonics, I am not surprised you could see repeating patterns.   If you average the crap out of it, you may find more detail.   

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