azonenberg changed the topic of #scopehal to: libscopehal, libscopeprotocols, and glscopeclient development and testing | | Logs:
<azonenberg> noopwafel: so not sure if you saw all the discussion but it turns out that they're fine
<azonenberg> there's not an impedance mismatch on the pcb, i overreacted to a single prototype with a bad solder job
<noopwafel> :D
<noopwafel> right I misread the later discussion, thought you'd already done one respin. nice!
<azonenberg> noopwafel: red = latest PT2
<azonenberg> gray = PT1 v1.3 as reviewed by TSP
<azonenberg> green = pico ta061 aka pmk "1.5 GHz" transmission line probe
<azonenberg> blue = lecroy zs1500
<azonenberg> cyan, pink = pico ta061 "6 GHz" transmission line probe with one or both ground pins making contact
<azonenberg> sorry i meant picoconnect 921 for cyan/pink
<azonenberg> noopwafel: what do you think, flat enough? :D
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<noopwafel> that is quite amazing
<azonenberg> Actual -3 dB BW exceeds the 6 GHz bandwidth of my VNA
<azonenberg> I intend to advertise it as a 6 GHz probe simply because i cannot characterize it past that
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<d1b2> <theorbtwo> Suggest advertising it as a ">= 6GHz" probe or "6GHz or better", becausr it will make some people (IE me) want to read more about it.
<azonenberg> Yeah I can say >6 confidently since 6.001 is still >6 lol
<azonenberg> in the datasheet specs I'll give min/typ/max s21 magnitude at several frequencies out to 6 GHz
<d1b2> <theorbtwo> I wonder if you could get Marco Reps to test it for you, in a "yo, I hear you like percision test equipment" sort of way.
<azonenberg> I will spec min S21 at 6 GHz as better than -23.5 dB (nominal at ~0 Hz is -20.5)
<azonenberg> I'm going to be sending one (or a few) to TSP
<azonenberg> So he can get me s-params out to 20 GHz
<azonenberg> but i'm obviously not going to be doing that for production
<azonenberg> i might use his number as a typical BW
<d1b2> <theorbtwo> TSP?
<azonenberg> then spec min of 6 GHz
<azonenberg> The Signal Path
<azonenberg> aka Shahriar Shahramia
<azonenberg> Shahramian*
<d1b2> <theorbtwo> Aha.
<azonenberg> He sent me s-params of the AKL-PT1 to 20 GHz from his review
<azonenberg> They track my picovna results fairly well to 6 GHz
<azonenberg> there's the big peak at ~5.3 GHz we already knew about then it drops off to -23.5 dB at 7.7 GHz. So right now the PT1 is a 7.7 GHz probe with a big hump in the response in the middle
<azonenberg> It's still plausibly usable until 10 GHz (-25 dB)
<azonenberg> then it nosedives, hitting -49 dB at 11.9 GHz. I believe this is the quarter wave null of the probe tip
<azonenberg> then after that it starts to act horrible as things begin to resonate
<azonenberg> If I were to respin the PT1 on ro4350b and switch back from enig to silver, i think i could buy enough loss margin that it would still be under 3 dB by 10 GHz
<azonenberg> and with any luck some of the recent layout changes will improve flatness
<azonenberg> beyond there performance will rapidly degrade because of the tip and there's not much i can do about that without major mechanical changes. At which point it's a new probe design
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