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Show us your square wave

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JPortici:
Finally the thing is repaired and i can play at this game too :D


unfortunately, the fastest thing i got at hand is the trigger output of a rigol scope, just under 1ns rise/fall time

well there is the 250 MHz ECL clock for the plugins.. and one has to be serviced......

Leo Bodnar:

--- Quote from: evb149 on April 29, 2017, 06:15:14 pm ---Also there are other sampler topologies that rely less on the matching of the components so that may be interesting to pursue.  I am not quite sure why Tek for instance only made a couple of samplers based on the travelling wave gate concept and used bridges for others.  It seems like it would be interesting to try a travelling wave design.

--- End quote ---
All Tek electrical sampling heads for 11800 and perhaps TDS8000 series scopes are based on what used to be called "travelling wave gate" in 11000 series (like S-4.) 
You can see them six sampling diodes here in the SD-26 sampling hybrid.
Leo

David Hess:

--- Quote from: Leo Bodnar on July 29, 2017, 11:32:22 am ---
--- Quote from: evb149 on April 29, 2017, 06:15:14 pm ---Also there are other sampler topologies that rely less on the matching of the components so that may be interesting to pursue.  I am not quite sure why Tek for instance only made a couple of samplers based on the travelling wave gate concept and used bridges for others.  It seems like it would be interesting to try a travelling wave design.
--- End quote ---

All Tek electrical sampling heads for 11800 and perhaps TDS8000 series scopes are based on what used to be called "travelling wave gate" in 11000 series (like S-4.) 
You can see them six sampling diodes here in the SD-26 sampling hybrid.
Leo
--- End quote ---

I think the traveling wave gate design still depends on matching and at least in my experience with the S-4, seems to suffer from more problems with blow-by.


--- Quote from: ADT123 on April 30, 2017, 08:39:55 am ---As for a lower cost / lower bandwidth sampling scope its an interesting idea.  Above a few GHz every component gets expensive if you want to do the job properly (connectors, PCB etc) but below say 5GHz things get a lot cheaper.  Will have a think.  Guess it depends on the market - hobby users often go for 2nd hand boat anchors which can be cheap and to be honest not everyone knows how to drive a sampling scope (splitters for trigger signals etc).
--- End quote ---

The report I have of a rebuilt Tektronix S-2 sampling head with cheap microwave schottky diodes from Avago was a improvement in bandwidth from roughly 4 to 8 GHz.  Tektronix used an RF substrate in that design but it was barely surface mount.

For signal integrity applications there are no special triggering requirements unless a clock is not available.  But the S-2 has an internal trigger pickoff so even that is not an issue.  Sampling the leading edge is of course a different matter requiring a delay line, pretrigger signal, or random sampling.

I am inclined to think the random sampling is the best way for ease of use however it makes for a very complex timebase and it does not work well with internal triggering.

Leo Bodnar:

--- Quote from: David Hess on July 29, 2017, 03:40:23 pm ---I think the traveling wave gate design still depends on matching and at least in my experience with the S-4, seems to suffer from more problems with blow-by.
--- End quote ---
To some extent all balanced samplers rely on matching the top and bottom paths - both in component parameters and electrical layout.  Travelling wave gate sampling aperture depends on physical distance between the middle and outside sampling diodes and on, say, SD-26 it is less than 1mm.  I won't be surprised if even diode bonding point position is critical.

I could not find any evidence of blowby compensation in SD-24 and SD-26 heads.  However, according to 11800 documentation some heads do have it.

nctnico:
ADF5341 ADF4351 + Agilent 54845A:


Edit: changed part number.

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