azonenberg changed the topic of #scopehal to: libscopehal, libscopeprotocols, and glscopeclient development and testing | https://github.com/azonenberg/scopehal-cmake, https://github.com/azonenberg/scopehal-apps, https://github.com/azonenberg/scopehal | Logs: https://freenode.irclog.whitequark.org/scopehal
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<azonenberg> i did some more modeling of the new-generation probe
<azonenberg> If i put a 9mm long stub with 30 ohm Z0 right past the resistor, i can attenuate most of the peaking
<lain> :o
<azonenberg> flat +/- 1 dB out to 3 GHz and +/- 2 dB out to about 5.5 GHz
<lain> nice
<azonenberg> this is entirely theoretical and some of the numbers are kinda guesstimated
<azonenberg> https://www.antikernel.net/temp/freqresp-newprobe.png this is my model of the new probe without any compensation
<lain> will be fun to see how close to theoretical that gets
<azonenberg> https://www.antikernel.net/temp/time-newprobe.png and this is (top graph) a 1.25 Gbps squarewave before compensation
<azonenberg> The bottom plot is the line being probed showing the reflection off the resistor through the probe tip
<azonenberg> so this is the interference the probe creates
<azonenberg> Running a time domain sim with compensation now
<azonenberg> This is all using a simple transmission line model derived from gerber dimensions and a caliper on the probe tip
<azonenberg> not a full field solver
<azonenberg> and vishay's published package parasitics for the resistor
<azonenberg> this is the model before compensation (added between Line3 and R1)
<azonenberg> https://www.antikernel.net/temp/time-withstub.png and this is time domain with the compensation stub
<lain> :3
<azonenberg> If i do indeed have awful peaking at high frequencies with the new probe i think i'll try and respin with the compensation stub
<azonenberg> Which would be my first actual use of "microwave black magic" in a pcb lol
<monochroma> XD
<monochroma> azonenberg: make sure to put a pentagram somewhere
<azonenberg> heck no, this is enough trouble to do with a manual parasitic extraction
<azonenberg> do you have any idea how to model a pentagram at RF? it must be a nightmare without a field solver
<monochroma> don't connect it :P
<monochroma> (also, silk screen)
<azonenberg> Yeah but it will still have nearfield effects
<azonenberg> what would be COOL is if you made a microstrip filter that actually had a pentagram as an active component
<monochroma> haha
<monochroma> model it with a scaled up version
<monochroma> (physical model)
* azonenberg imagines a giant satanic altar inside a faraday cage with a bunch of coax connected to one side of it
<monochroma> lol
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<bvernoux> hello
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