Author Topic: 10 GHz USB Oscilloscope  (Read 30107 times)

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Offline eurofox

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Re: 10 GHz USB Oscilloscope
« Reply #50 on: June 06, 2014, 01:11:36 pm »
I got the DS800E 11 Ghz version.

I did many test on pulses and RF and work very well.

Of course it is a sampling scope, only for use with repetitive signals.

I compared my test with a Tek TDS820 (6 Ghz) and Agilent MSO-X (1Ghz) and got similar results.

The software could be improved but I think this will be done.

Good value for the money.

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Offline fcb

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Re: 10 GHz USB Oscilloscope
« Reply #51 on: June 08, 2014, 10:30:49 pm »
Can you post some pictures Eurofox. What's the build quality like? How was the delivery time?
 

Offline eurofox

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Re: 10 GHz USB Oscilloscope
« Reply #52 on: June 08, 2014, 10:57:30 pm »
Can you post some pictures Eurofox. What's the build quality like? How was the delivery time?

I intend to make a review, pictures, test with different sources (pulses in the ps second range, RF ....), I just order a 10 Ghz VCO.

I'm really surprise, this little scope perform very well.

Some work to do on the software to improve it but I will manage that.

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Offline yramgu

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Re: 10 GHz USB Oscilloscope
« Reply #53 on: June 09, 2014, 09:20:28 am »
Im very much looking forward to your review eurofox :)
Might get myself one of these
 

Offline Gall

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Re: 10 GHz USB Oscilloscope
« Reply #54 on: June 20, 2014, 01:50:43 pm »
I hope the price for ADC12D2000 will drop one day... Now it is $4,499 at Digi-Key.  :-BROKE
The difficult we do today; the impossible takes a little longer.
 

Offline David Hess

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Re: 10 GHz USB Oscilloscope
« Reply #55 on: June 21, 2014, 06:16:33 pm »
The "sampling head" on the analog input is made from an comparator (ADCMP582), the trigger input is using ADCMP567. The max. sample rate is defined by the delay line resolution (on DS800 that 1ps) and the 12bit vertical resolution. Therefore is the maximum sample rate, for DS800, ~ 83GS/s

Based on photo that is not how it works and an ADCMP582 is not nearly fast enough to support that kind of input bandwidth.  The two sampling inputs are at the bottom next to what I assume are a pair of RF mixers repurposed as sampling bridges.  The four inputs at the top going to the comparator are the trigger inputs.  This is a traditional sampling oscilloscope design.
 

Offline David Hess

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Re: 10 GHz USB Oscilloscope
« Reply #56 on: June 21, 2014, 06:21:05 pm »
I'm aware of how equivalent time sampling works. But you did answer my question, it is as I feared... use the PIC for sampling. I don't quite understand why he would go to the trouble of making a nice frontend etc, and then use such a limited actual, non-equivalent, quite real sampling rate of 500 ksps. High speed at 12-bit isn't all that expensive.

If you have a signal that has reasonable but not great long term stability, then you can make do with equivalent time sampling as long as you don't take eons to gather all your samples. However I can see the use case for this where 500 ksps is sufficient (checking SI on your pcbs etc). It's only too bad IMO, because even a lowly 40 MSPS 12-bit ADC would be a nice improvement. That said, even with the 500 ksps limitation this looks quite interesting.

Sampling rate is limited either by the maximum strobe rate like if the strobe is generated by an avalanche pulse generator or the delay time generator or counter which has to reset between samples.  Higher sample rate designs grab multiple samples along a transmission line with one strobe as with the linked LLNL design.

My sampling oscilloscope only operates at about 50 ksps and is completely usable providing a real time display into the 10+ GHz range.
« Last Edit: June 21, 2014, 06:52:18 pm by David Hess »
 

Offline David Hess

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Re: 10 GHz USB Oscilloscope
« Reply #57 on: June 21, 2014, 06:26:55 pm »
It's optimistic to say I could do it ... but it's not optimistic as in not physically feasible, they did it all with commodity parts 20 years ago.

My sampling oscilloscope is old enough to drink. :)

Quote
If you can avoid the truly low (<0.1pf) capacitance diodes and use one of the non exotic RF schottkys from a mainstream manufacturer you're only going to be out around 100$ for 1000 diodes.

Avago sells the needed diodes to get into at least the 4 to 6 GHz range and they are cheap.  The strobe generator and timing circuits are much more difficult.
 

Offline David Hess

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Re: 10 GHz USB Oscilloscope
« Reply #58 on: June 21, 2014, 06:36:29 pm »
PS. unless you can find some really low cost way to make a 100 ps range pulse generator, so you can have one pulse generator per tap ... then you could do coarse delay in a FPGA, fine tuned with a varactor circuit (and on-line calibration).

An FPGA would need to be dedicated if used in the strobe or trigger critical path because of pattern dependent jitter and FPGA time to digital converters have pretty low resolution compared to the alternatives although they are mighty fast.

Time to voltage conversion could do better than 10ps over 50ns 20+ years ago so I would be disappointed in a modern design which could not interpolate within 1ps while using a 50 or 100 MHz counter.  ECL logic was used back then and I would expect it to be used now in the critical paths.
« Last Edit: June 21, 2014, 06:48:23 pm by David Hess »
 

Offline David Hess

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Re: 10 GHz USB Oscilloscope
« Reply #59 on: June 21, 2014, 06:46:41 pm »
I'm getting the impression you've never used a sampling scope before.  Sampling scopes require a trigger clock input, including the scope we're discussing here, which can be generated by splitting the input waveform into two -3 dB signals.  The scope triggers off this clock and not from another clock (such as an internal 10 MHz) that has no relation to the input signal.  If there is phase noise in the clock, you will still see the clock waveform on the scope, and then you will be able to see that the edges of the waveform are fuzzy from the phase noise or jitter.  This is actually useful information for debugging your circuit and will inform you that you have a phase noise problem.  If you then put the input signal through an amplifier, you will fully be able to see how the amplifier has affected the signal.  If the amplifier is oscillating or having a drastic problem, then you will see noise instead of a clean, amplified signal.  This will also tell you that there is something wrong with your circuit, and when it comes out as a clean, amplified signal, then you know your circuit is working.
I understand your point it's a convincing one and You are right I've never use this type of scope before. If I may say so, It seems more usefull as a production test scope.

Just to give an example of what can be done, here is an oscillograph from my sampling oscilloscope loafing at 200 ps/div while measuring pattern dependent jitter in a TTL delay circuit that I was testing.  Sample rate is about 50 kSamples/second.  A standard CRT display was completely adequate for mark 1 eyeball use despite the low sample rate but in this case a CRT storage display was used to make a better photograph.    Measurement jitter is insignificant on this scale at about 10ps.
 

Offline Marco

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Re: 10 GHz USB Oscilloscope
« Reply #60 on: June 22, 2014, 01:40:21 am »
The "sampling head" on the analog input is made from an comparator (ADCMP582), the trigger input is using ADCMP567. The max. sample rate is defined by the delay line resolution (on DS800 that 1ps) and the 12bit vertical resolution. Therefore is the maximum sample rate, for DS800, ~ 83GS/s
Based on photo that is not how it works and an ADCMP582 is not nearly fast enough to support that kind of input bandwidth.

He didn't say anything about the bandwidth, he said the maximum (equivalent) sample rate is 83 GS/s.
Quote
The two sampling inputs are at the bottom next to what I assume are a pair of RF mixers repurposed as sampling bridges.

The package is a match for the ADCMP582 and pin 3 on the ADCMP582 is the negative input ... and I would not expect mixer diodes in such a package.
« Last Edit: June 22, 2014, 01:47:54 am by Marco »
 

Offline David Hess

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Re: 10 GHz USB Oscilloscope
« Reply #61 on: June 22, 2014, 04:54:49 am »
It looks like you are right.  I had to check the datasheet but it shows that the ADCMP582 has an input bandwidth of 8 GHz.  That explains why that sampling design has such a slow sampling rate but on the other hand does not need a strobe driver or sampling bridge.  Discrete versions of the later can certainly achieve higher sampling rates and bandwidth in a surface mount design but the strobe is is not trivial.

There are some RF mixers in similar packages which might work as sampling bridges.
 


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