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Video Teardown & Experiements with LeCroy's 100GHz, 240GS/s Scope

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EEVblog:

--- Quote from: vaualbus on February 13, 2015, 01:15:08 am ---Ok so my comment on youtube about the price of the board have to be modify. This can cost a fortune (surly more than 5k) also why soo many layer? a lot of digital signals?
 I have never  hear  about 28 a layer board before! Amazing.

--- End quote ---

At these sorts of rates signal integrity is everything. That happens best with ground planes and lots of them.
Then you have the huge BGA parts that need fanning out.
You also have huge power requirements whcih also calls for many power planes, and there will be many power rails, 5 or 6 power rails in a high speed digital domain is not uncommon.
Fanning out a big arse BGA package usually takes 6-8 signal layers, and if you whack a ground plane between each one of them, that's 16 layers right there off the bat. Add another half dozen for big power rails and misc routing and you can start to see how you might need 28 layers.

Wuerstchenhund:

--- Quote from: vaualbus on February 13, 2015, 01:15:08 am ---So do you know if keysighy is keysight is developing a scope for that range of frequency?
--- End quote ---

They are probably trying, but I doubt we will see anything like that from Keysight for the next 5 years or so.

And if they finally come out with their own 100GHz scope it probably will be a (non-expandable) 4 channel scope that only reaches 100GHz on one or two channels only.

LeCroy's LabMaster 10-100ZI can provide up to twenty 100GHz channels or up to eighty 36GHz channels. Even aside from the huge bandwidth, the LabMaster is a complete different beast than anything that is offered by Keysight or Tek.


--- Quote ---also at the beging the guy that explain the theory said that there are company made these oscilloscope. Keysight lecroy and tektronix right? Because the top model of tek scope go up to about 30ghz

--- End quote ---

He said that there are only three manufacturers of High Speed Oscilloscopes (i.e. oscilloscopes with high sample rates of 40GSa/s or more), which are LeCroy, Keysight and Tek.

Tek has been stuck at 33GHz for some time while LeCroy and later Agilent made the jump to 65GHz and (in case of LeCroy) now 100GHz, and it's unlikely that will change anytime soon.

rx8pilot:

--- Quote from: EEVblog on February 13, 2015, 06:05:40 am ---
--- Quote from: vaualbus on February 13, 2015, 01:15:08 am ---Ok so my comment on youtube about the price of the board have to be modify. This can cost a fortune (surly more than 5k) also why soo many layer? a lot of digital signals?
 I have never  hear  about 28 a layer board before! Amazing.

--- End quote ---

At these sorts of rates signal integrity is everything. That happens best with ground planes and lots of them.
Then you have the huge BGA parts that need fanning out.
You also have huge power requirements whcih also calls for many power planes, and there will be many power rails, 5 or 6 power rails in a high speed digital domain is not uncommon.
Fanning out a big arse BGA package usually takes 6-8 signal layers, and if you whack a ground plane between each one of them, that's 16 layers right there off the bat. Add another half dozen for big power rails and misc routing and you can start to see how you might need 28 layers.

--- End quote ---

I have never done a layer count like that but I remember talking to an engineering group doing some very high speed layout in the neighborhood of 28 layers. One interesting comment they made was that the PCB yield was rather low. The very fine traces mixed with blind and buried vias apparently get s very difficult to manufacture. It only takes one via (out of 10's of thousands) that does not make contact to make a rainy day. If the via is buried, or its a critical path, there may be no bodge wire option.

VK5RC:
Thanks Shariar and Lecroy,  I liked the rf deck,  those connectors and lines are very special,  coax over 20GHz is pretty special, phase,  impedance matching,  was the figure below 50 fS? Light travels just ^0.1mm. Thanks

electr_peter:

--- Quote from: coppice on February 13, 2015, 05:53:50 am ---
--- Quote from: electr_peter on February 12, 2015, 09:58:47 am ---One thing I really like about such scope is that it is pushing the limits. It gets to 100 GHz, but just barely (almost all aspects are pushed to the limit, only extensive DSP corrections helps to keep it in one piece). I am sure a small amount of tweaking could bring another GHz or so for current model and future versions will be even better.
It is certainly not the case of having 200 GHz BW scope and configuring it via some jumpers to "entry range" 100 GHz BW version.

--- End quote ---
Why do you say "just barely"? It gets to 100GHz by old and well tried techniques, implemented with state of the art hardware. It will be a lot quirkier than a straightforward monolithic ADC. Anything large has thermal tracking issues, and anything that that many separate parts working in concert is going to have calibration issues. The calibration can be handled very well by modern approaches.

--- End quote ---
I mean to say that this scope is using many of components to the max specs while components are high speced to begin with. Not much headroom is left. Paper linked in this thread also shows that frequency response starts to roll of at higher frequencies. Triggering is harder to implement because of many steps involved in analog->digital path.

One of the main problems is a low BW and low sampling rate of ADCs. They solved it by interleaving multiple ADCs. BW limitations of ADC is solved by interleaving splitted and downconverted frequency bands. You can call this solution quicker than new high BW ADC but I think it is a bypass of current ADC limitations to get to full 100 GHz BW.


--- Quote ---They make a 100GHz oscilloscope because that's what the optical people (who are the main market) want. If the optical people say they need 200GHz or 300GHz and have the budget, LeCroy should have no problems extending the current design to those bandwidths. Beyond 300GHz  or so life starts to get more interesting. :-)

--- End quote ---
100 GHz version is made because they can do it, they need to compete and innovate, it is needed for industry and research applications. I have no doubts that slightly higher BW version can be made with similar architecture, but it will be more and more difficult for them because of front end limitations.

Do you think they can make 200 GHz scope by using two 100 GHz scopes and using similar frequency splitting technique? I don't think it is possible now, more R&D is needed to boost front end BW.

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