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impedance measurement with VNA using series, shunt/series through methods, graph

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joeqsmith:

--- Quote from: JohnG on May 24, 2021, 12:14:38 am ---My career started designing RF amps, ..

... This is all work-related. The challenge is that I don't have the luxury of 50 ohm anything. Since they are power conversion circuits, a lot of amps are flowing around at low voltage, so the impedances are generally much lower than 50 ohms.

Cheers,
John

--- End quote ---

I was with you up to that last sentence.  There are many good educational videos on using 50 ohm systems to measure PDNs.  This thread hardly scrapes the surface.  In many videos, they will demonstrate simulation software available today.   You may enjoy watching some of them. 

My old HP3589A isn't good enough to look at that 100uOhm directly.  My goal is to eventually try and use the Nano to measure a circuit boards PDN.  Now that we have a transformer and DC blocks, it's back to software.   In my case, it's just for the fun of it.   

I have one of Pearson's transformers.  The patents were helpful in understanding how they pulled it off.   Years back, I read this article and tried to replicate their results.     
https://interferencetechnology.com/the-hf-current-probe-theory-and-application/


JohnG:
I'm not measuring PDNs in the traditional sense, though there is a fair bit of overlap. I am trying to model small, very fast switching high-current circuits that might be coupled or attached to a PDN intentionally or otherwise. An imperfect analogy would be that PDN analysis tends to look at things macroscopically, and I need to look more microscopically.

Also looking at simulation software, but the expense is significant so I need to make sure it will meet current and anticipated future needs, and I have very little 3D simulation experience. The other problem is that to really get good at such a tool, it helps to have an experienced employee to go with it.

Cheers,
John

 

joeqsmith:

--- Quote from: JohnG on May 24, 2021, 02:00:02 pm ---I am trying to model small, very fast switching high-current circuits that might be coupled or attached to a PDN intentionally or otherwise. An imperfect analogy would be that PDN analysis tends to look at things macroscopically, and I need to look more microscopically.

--- End quote ---

Sorry but you would need to provide more details for me to follow.  I consider macro as being something large and micro as small.  You wrote how you want to look in the mOhms where I have posted looking in the uOhms.  Oh wait, it was an imperfect analogy.   :-DD 


coppercone2:
you can try to measure the same value 10 times and graph the plot in all the measurements to see the spread, it might have to do with the confidence interval

JohnG:

--- Quote from: joeqsmith on May 24, 2021, 11:05:28 pm ---
Sorry but you would need to provide more details for me to follow.  I consider macro as being something large and micro as small.  You wrote how you want to look in the mOhms where I have posted looking in the uOhms.  Oh wait, it was an imperfect analogy.   :-DD

--- End quote ---

I'll try to make it better. A PDN is more of a system level concern, basically a network with a lot of objects (sources and loads, loosely speaking). The objects could be a capacitor, an IC with bypassing, a switch-mode converter, etc. I'm looking at switch-mode power stages, which might feed a PDN. Such a stage will have caps, controls, active and passive parts, so tends to have complex behavior on its own. So a person looking from a PDN point of view tends to view these as given impedances on the network, but I zoom in on these details and others, so to speak. The other details relate to power dissipation, power processing density, cost, safety and reliability, etc.

Cheers,
John

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