Products > Test Equipment
Affordable <200MHz PDN analysis / impedance measurement hardware?
inevitableavoidance:
--- Quote from: rhb on November 12, 2024, 10:20:38 pm ---An HPAK 4395A is reasonably priced and had a very long life, so plentiful. I’m using one to develop EMI filters to suppress conducted noise from my LED shop lighting.
It will really get a workout when I start building the screen room feeds.
I really can’t see how you can improve on the price - performance. I love it. Best possible tool for the frequency range of interest. It’s both a VNA and an SA with 1 Hz resolution. It covers 10 Hz to 500 MHz. For HF work it’s the king.
Designing appropriate fixtures and calibration standards for testing boards won’t be easy. You’ll need machine tool access. Helps a lot if you design in test points. Low impedance fixtures are likely to be “interesting” to make. But then the challenge is the whole point for a lot of projects.
Have Fun!
Reg
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That does look like the absolute perfect measurement range - a bit out of my initial budget but I’ll definitely keep an eye out for a good second hand deal. Test fixtures and connections are quite a world of their own I have indeed found. So far I’ve had most luck simply stripping and soldering on microcoaxial cables. I wish someone would make and standardise a miniature “kelvin” RF connector for this
tszaboo:
--- Quote from: inevitableavoidance on November 12, 2024, 10:23:24 pm ---
--- Quote from: tszaboo on November 12, 2024, 09:59:02 pm ---Your circuit is quite interesting. Any reason you decided to AC couple the signals instead of accepting the small DC offsets?
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Thanks! When for example measuring the output impedance of a buck converter under load the DC bias will be equal to the output voltage, so for measurements like this being able to handle high DC offsets is essential
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Ah, you want to measure it while on, not like with the VNAs. I believe a power rail probe is more suited for a measurement like that. I made a power rail probe, goes to 2GHz, no gain though. But with the small noise coming from it, you should be able to directly measure a few mv signals. And gain can be added by any 50 Ohm input/output amplifier.
Now, I'm not trying to sell you my probe, just want to give you some pointers, if you are interested.
rhb:
Don’t underestimate a DSO with memory and a decent sig gen. Suck the data into Octave for analysis. The really hard part is a low frequency directional bridge. I suggest reading up on slotted lines and how the microwave pioneers coped. Measurements at multiple points on a delay line should handle direction separation.
If time is more plentiful than money, even the 20 kPt Hanmatek DSOs made by Owon and lots of measurements will do the job. Use what you have.
Most of my life I was not willing to spend money on what were “toys”. At 71 I now spend it. But I learned a lot working around no budget. So I urge doing that very strongly. It reinforces being able to work from first principles. That was ALWAYS valuable.
Have Fun!
Reg
BTW Join the T&M list on groups.io. The eBay prices are rather stiff. And be patient.
joeqsmith:
--- Quote from: tszaboo on November 12, 2024, 10:43:45 pm ---Ah, you want to measure it while on, not like with the VNAs.
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?
nctnico:
--- Quote from: rhb on November 12, 2024, 11:12:51 pm ---Don’t underestimate a DSO with memory and a decent sig gen. Suck the data into Octave for analysis. The really hard part is a low frequency directional bridge.
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Why would you want to use a directional bridge? For PDN you use a 2 port measurement AFAIK. Push AC current into the DUT from the transmitter port (generator) and measure the resulting AC voltage across the DUT.
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