Hacker News Reader

Comment by KK7NIL | Hacker News Reader

A Keysight UXR can do one quarter of that, 256GS/s, but a Tektronix 6 series is limited to 25 GS/s iirc, so you're right.

View on HN

Looks like max 50GS/s per their site. That also looks reasonable with the screenshot they have in the article showing 1ns / div horiz. But clarity on the data would be lovely. =)

Actually I take it back: For the series 6B spec page... Real-time: 50 GS/s (2 channels), 25 GS/s (4 channels), 12.5 GS/s (> 4 channels) Interpolated: 2.5 TS/s

Yeah, I used to work at Tektronix, this looks like an A unit.

Also, the 50GS/s is actually more like 25GS/s as it has a Nyquist frequency of 12.5 GHz. This is because they take 2 samples at the same time, instead of 180 degrees out of phase. I wish they had made that clearer to customers, it felt misleading to some.

If you are an absolute nutcase, you could characterize a set of line stretchers and a multiplexer on a high end VNA then offset the inputs of the 4 channels on that UXR with them, take a capture and finally rebuild a 1TSamp/s signal out of the 4 results.

You have to have the 240V model of the scope to run all four channels at full rate (110GHz) though.

The older Tektronix TDS540 series did this, but at much lower rates as was common in those days though. Internally there are differential feeds from the very beautiful hybrid ceramic input boards to 4 DACs, with some clever switching so that a single input can be sampled by all 4 DACs with a suitable offset to create 4x the sample rate when running with all 4 inputs.

The calibration procedure on the scope fiddles with the time alignment to get the different DACs correctly offset so that the combined signal is correct.

The hybrid ceramic input boards in their metal cases are a thing of beauty, fragile (don't ask how I know), but beautiful.

Yup, a lot of scopes actually did this internally and some still do. It's part of why some scopes lose half their BW when you go from 2 ports to 4 ports (some go the other direction and run multiple ports on one very fast ADC), they split the digitizers. It's just very very difficult to keep it working external to the box mainly because of line drift.

Take that Nyquist ;)

Reply on news.ycombinator.com