Author Topic: The end is near. LeCroy and their 100GHz scope...  (Read 19898 times)

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Offline dannyf

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Re: The end is near. LeCroy and their 100GHz scope...
« Reply #50 on: June 14, 2014, 05:49:12 pm »
Quote
they are using a 16.6 GHz signal generator and a six times multiplier,

What about using a sub-pico-second pulse generator and filter out the lower harmonics?
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Offline SeanB

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Re: The end is near. LeCroy and their 100GHz scope...
« Reply #51 on: June 14, 2014, 05:57:33 pm »
Pulse repetition rate is too low..............
 

Offline Dave Turner

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Re: The end is near. LeCroy and their 100GHz scope...
« Reply #52 on: June 14, 2014, 09:42:53 pm »
The technology is there: there are optical amplifiers for fiber transmissions.

Dannyf - that was sort of my point.

To my knowledge serious research has been going on to create optical devices analogous to semiconductors at least as far back as the 70's, if not further. I'm not counting holographics. Where said research has got to I don't know, however given that the research is successful, becomes commonplace and miniaturised we should see an increase of several orders of magnitude in high speed computation. transmission etc. Hopefully in what's left of my lifetime.
 

Offline Alex Eisenhut

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Re: The end is near. LeCroy and their 100GHz scope...
« Reply #53 on: June 15, 2014, 03:40:26 am »
How do you even generate that 100 GHz test signal? Jesus, that's a tenth of a terahertz! :scared: DC to daylight indeed...

I swear, at the rate we're going, we'll have scopes that can probe literal daylight by the time I'm 40...

Probably RTD based. BWO's been doing that for decades. They go to THz.

As for a "scope" with a light input, why did you wait so long?

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Offline Alex Eisenhut

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Re: The end is near. LeCroy and their 100GHz scope...
« Reply #54 on: June 15, 2014, 03:42:04 am »
How do you even generate that 100 GHz test signal? Jesus, that's a tenth of a terahertz! :scared: DC to daylight indeed...
There is a newer video where they explain how they generate a test signal, and some more background information:

He says that there is no test equipment that can generate a 100 GHz sine wave, so they are using a 16.6 GHz signal generator and a six times multiplier, feeded to the scope through a wave guide (see video 1:40). Doesn't look like a standard BNC :)

They don't say how much the scope costs, but of course it is too expensive if you have to ask.

"no test equipment that can generate a 100 GHz sine wave"? Really?

"Doesn't look like a standard BNC"

1mm connector goes to 110GHz. Wonder why they make 'em if no one can generate 100GHz....
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Offline Alex Eisenhut

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Re: The end is near. LeCroy and their 100GHz scope...
« Reply #55 on: June 15, 2014, 04:15:14 am »
The technology is there: there are optical amplifiers for fiber transmissions.

Doped fiber amplifier. It's all done in the physics of light. Not "electronics" in the traditional sense, although it's all done with electrons one way or another...

http://en.wikipedia.org/wiki/EDFA

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Offline Wuerstchenhund

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Re: The end is near. LeCroy and their 100GHz scope...
« Reply #56 on: June 15, 2014, 11:16:02 am »
Ever since the whole "12 bit" scope marketing exaggeration they did

What '"12 bit" scope marketing exaggeration'?
 

Offline Noise Floor

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Re: The end is near. LeCroy and their 100GHz scope...
« Reply #57 on: June 15, 2014, 04:12:39 pm »
Ever since the whole "12 bit" scope marketing exaggeration they did

What '"12 bit" scope marketing exaggeration'?

They pushed very hard the fact that they used a 12 ADC compared to other market competitors using 8 bit ADCs.  The problem I found is what I spoke to above, the extra ADC resolution was only useful in a very narrow band.  I believe this was a result of the scope not being engineered for 12 bits throughout as well as the ADC itself having lots of noise and distortion at many input frequencies. 

Our lab at work bought an HDO early on I learned to not trust it pretty quickly relative to other scopes I have access to, for the applications I was working on.  I bold that part because I do think the extra resolution could be used in certain settings, but people should know the limitations of all their equipment and not buy into the marketing of 12 bit always being better.  That said, I did really like the UI and footprint of the scope and I think Lecroy innovated well in that space.  I just don't care for over the top exaggerated marketing, which this 100GHz demo smells like to me, although I can't claim that for certain.
 

Offline Wuerstchenhund

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Re: The end is near. LeCroy and their 100GHz scope...
« Reply #58 on: June 15, 2014, 06:22:08 pm »
Ever since the whole "12 bit" scope marketing exaggeration they did

What '"12 bit" scope marketing exaggeration'?

They pushed very hard the fact that they used a 12 ADC compared to other market competitors using 8 bit ADCs. 

Well, that's what marketing is about, highlighting where your product is different/better than the competition. At the end of the day, marketing *is* exaggeration. It's not just LeCroy doing it for their scopes, everyone does it.

This aside, LeCroy did have a point: Agilent's pseudo 12bit scope was indeed using 8bit ADCs with oversampling. Nothing wrong with highlighting that.

And if you really believe that LeCroy was exaggerating then I would really like to hear what you think about Agilent quite often in their marketing brochures ('whitepapers') twists reality 'til it screams.

Quote
The problem I found is what I spoke to above, the extra ADC resolution was only useful in a very narrow band.  I believe this was a result of the scope not being engineered for 12 bits throughout as well as the ADC itself having lots of noise and distortion at many input frequencies. 

Our lab at work bought an HDO early on I learned to not trust it pretty quickly relative to other scopes I have access to, for the applications I was working on.  I bold that part because I do think the extra resolution could be used in certain settings, but people should know the limitations of all their equipment and not buy into the marketing of 12 bit always being better. 

I agree, but that is no different with other scope properties, every engineer should know how important certain features are for his specific applications, that's part of the job.

To me this sounds like your place simply bought the wrong tool for the job, which does happen (this is why most scope manufacturers do offer lending a scope for a short time for evaluation). And quite frankly, any person that blindly buys a new and very expensive piece of test equipment without making sure it's beneficial for the application or making use of getting a loaner first should be 'promoted' to cleaning the lab floor.

Quote
That said, I did really like the UI and footprint of the scope and I think Lecroy innovated well in that space.  I just don't care for over the top exaggerated marketing, which this 100GHz demo smells like to me, although I can't claim that for certain.

Again, if you think LeCroy is exaggerating (which is a bit difficult in such a live demo, especially if there is a certain reputation to protect) then go and have a read through some Agilent whitepapers.
« Last Edit: June 15, 2014, 06:24:37 pm by Wuerstchenhund »
 

Offline Noise Floor

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Re: The end is near. LeCroy and their 100GHz scope...
« Reply #59 on: June 16, 2014, 05:48:17 pm »
Hey Wuerstchenhund,

You won't much disagreement from me with what you said.  I'm not familiar with the white papers you are referring to, perhaps we should create a thread for "marketing wall of shame".  I was only speaking to my experience in this case and have strong memory of being hitting over the head with "12-bit!" marketing emails and ads for a while. :)
 

Offline Wuerstchenhund

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Re: The end is near. LeCroy and their 100GHz scope...
« Reply #60 on: June 16, 2014, 07:36:13 pm »
perhaps we should create a thread for "marketing wall of shame". 

That would be futile, as the list would certainly be endless. It's much easier to only list the positive examples, as this makes for a rather short list  ;)

Quote
I was only speaking to my experience in this case and have strong memory of being hitting over the head with "12-bit!" marketing emails and ads for a while. :)

Don't forget that marketing has a purpose, not only for the manufacturer that wants to sell its goods. Simply because for expensive kit the person who wants it is often not the person who pays for it. An engineer may want a certain scope but if he can't convince his finance controller that this is the best thing since sliced bread then he simply won't get it. Sad but true in many workplaces. Marketing is the bait engineers use to get what they want  8)
 

Offline Noise Floor

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Re: The end is near. LeCroy and their 100GHz scope...
« Reply #61 on: June 21, 2014, 07:45:01 pm »
Don't forget that marketing has a purpose, not only for the manufacturer that wants to sell its goods. Simply because for expensive kit the person who wants it is often not the person who pays for it. An engineer may want a certain scope but if he can't convince his finance controller that this is the best thing since sliced bread then he simply won't get it. Sad but true in many workplaces. Marketing is the bait engineers use to get what they want  8)

I never thought of it that way, very interesting.
 

Offline David Hess

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Re: The end is near. LeCroy and their 100GHz scope...
« Reply #62 on: June 22, 2014, 08:21:38 pm »
There are whole books on oscilloscope front end design?? Any you can recommend? I'd love to see if I can find one...
Well not front end design specifically, but with chapters devoted to it ... can't vouch for the quality, but this is what I found :

Art and Science of Analog Design by Steve Roach
Wideband Amplifiers by P. Staric

Both concerning relatively low (<GHz) bandwidth designs BTW ... old tech, which can be build with discretes.
I thought of that article as well.  It is included in "The Art and Science of Analog Circuit Design (EDN Series for Design Engineers)" edited by Jim Williams:

http://www.amazon.com/Science-Analog-Circuit-Design-Engineers/dp/0750670622

"Analog Circuit Design: Art, Science and Personalities (EDN Series for Design Engineers)" which was also edited by Jim Williams discusses oscilloscope vertical amplifier design among other things.

http://www.amazon.com/Analog-Circuit-Design-Personalities-Engineers/dp/0750696400
 

Offline David Hess

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Re: The end is near. LeCroy and their 100GHz scope...
« Reply #63 on: June 22, 2014, 08:42:10 pm »
Ah okay, yeah I read about that in some books on oscilloscope front end design ... basically the ideal HF amplifier is a source/emitter follower, but they have lousy 1/f noise and DC offset stability, whereas opamp circuits have great 1/f noise and DC offset stability.

Unfortunately oscilloscopes are stuck using source followers for high and controlled input impedance and good transient response.  The DC stability in operational amplifiers comes from a fully differential input and it is worth noting that analog oscilloscopes do a single ended to differential conversion early in their signal chain to take advantage of this.  Some (most?) DSOs do as well.

The 1/f and other noise is not helped by using small area devices to limit input capacitance for good high frequency performance.
 

Offline Sailor

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Re: The end is near. LeCroy and their 100GHz scope...
« Reply #64 on: June 23, 2014, 10:58:52 am »
The Tektronix  book 'Vertical Amplifier Circuits' is great reading.
 


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