Agilent 62Ghz scope Demo and experiments

The million-dollar oscilloscope can't be far away.

And a $350 Rigol is a better scope than something that cost $10K not too long ago.

--

John Larkin         Highland Technology, Inc 

jlarkin at highlandtechnology dot com 
http://www.highlandtechnology.com 

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom laser drivers and controllers 
Photonics and fiberoptic TTL data links 
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Hi,

Wow thats a nice $500,000 scope.. It also looks like something that could be homebuilt! :) Its a 4channel 80GSPS, looks like 8x interleaving per channel, so that would be 8 10GSPS ADC's (8bits each) per channel. The hard part might be getting the low jitter clock running to feed the ADC's for interleaving them, but the phase delay on the interleaving once set correctly via fine tuning of the trace length or whatever should be doable I guess! Sounds like a fun weekend project!

cheers, Jamie

You usually need to electronically tune the aperture delay. BTDT. Not at

10GHz but "only" 100MHz or so and 12-bits. However, the client didn't want to see any residual stuff down to -100dB which made this a nice challenge.

--
Regards, Joerg 

http://www.analogconsultants.com/

What about Lecroy's 100GHz scope? :-)

--
Gruss, Mark

That is a bit slow :-)

How do you troubleshoot 40 Gbit/s optical link systems ?

Apparently with repeated patterns and subsampling ?

Hi,

Would it be possible to use something like a tank circuit as a jitter reducer on a cheap clock? Like if the tank circuit operates at the same average frequency as a clock, it can store energy for more than one cycle and lock in the frequency perhaps so there is less jitter and the cheap clock source could keep the tank circuit energized, this would be a 1GHz to 10GHz tank.

cheers, Jamie

Turd-polishing like that can help a bit in marginal situations, but it's far from a complete solution.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 USA 
+1 845 480 2058 

hobbs at electrooptical dot net 
http://electrooptical.net

It works differently. You take a super squeaky clean clock, goes into a divider, send one of the divider outputs through a fixed delay network and then on to the first ADC. The others get theirs via electronically adjustable delays. Best to use a servo structure in there so the processing math workload is low, resulting fast convergence. Then send a test signal through there with an odd divide ratio and lowpass it a bit. For example, a divide ratio of 9 if you have 8 ADCs. Now the 2nd ADC's delay circuit is adjusted until the 9th conversion result is the same as the 1st, the 3rd ADC's circuit until the 18th result is the same as the

1st, and so on.

--
Regards, Joerg 

http://www.analogconsultants.com/

Hi,

Thanks for the info, I guess the interleaving is another area that reduces these high speed scopes sensitivity, since the signal is fed in parallel to all the interleaved channels, the input impedance isn't infinite on the inactive inputs, so the impedance of the scope goes down with interleaving. Maybe there is a plasmonic chip design out there hat runs synchronous with the ADC sample clock and is like a plasmonic relay to cut off the inactive ADC's at the right time and increase the scopes input impedance. Or else some 1THz+ mosfets back to back on each ADC input to act as input switches, maybe this is already done, it seems like 8 interleaved channels would reduce the sensitivity of the scope too much otherwise?

cheers, Jamie

I doubt it. There will be amplifiers and buffers. Aside from the sensitivity issue there is also the fact that this oscilloscope will not be exempt from having to pass EMC regulations. An ADC with its input piped out directly would usually result in guaranteed failure because the clock spews out. Nowadays it's measured up to 6GHz but even if it was above, customers would not appreciated if a new piece of equipment pollutes the RF stuff in their lab.

Nah, they are usually run all in parallel. But there are buffers before each ADC and in front of that another amplifier. In a scope you've got to, because the input range of a typical ADC is much too wide and a scope must be able to get down to 20mV/div or less.

There is another reason for buffers. If you hang ADC inputs parallel they will disturb each other. That can cause auto-calibration routines in a stagger-scheme to not converge or go bonkers.

--
Regards, Joerg 

http://www.analogconsultants.com/

Sounds interesting. How do you get -100dB with 12 bits? Would need at least 17 bits. A moving average filter could work:

But I guess for the extra 5 bits you would need 32 times the sample frequency?

--
Frank Buss, http://www.frank-buss.de 
electronics and more: http://www.youtube.com/user/frankbuss

In this case it was Doppler processing. The bandwidth of the information was much lower than in normal aquisition mode (which was also used) and then you average over many samples plus over time. How much SNR increase will result depends mostly on the length of the pulsed Doppler receive window which is called range gate. The actual gating electronics are often also called range gate.

For this to work the ADCs need to be super-duper quiet, much more so than they'd have to be for the normal 12-bit work. This also means that the phase jitter that such an auto-calibration shifter introduces has to be as much down as your full averaged SNR.

An example how tough this can be: A client had a noise problem in a similar system. Just a faint line on the FFT. But it annoyed their end customers. Before they called me they had tried the most expensive spectrum analyzers on it but could not find anything. So I showed up with a receiver and head phones. The only way to find it was with the receiver switched to singel-sideband reception and slowly turning the dial through a large swath of frequencies. Because in a Doppler system everything folds into the spectrum at the pulse repetition frequency, which makes noise hunting tedious.

--
Regards, Joerg 

http://www.analogconsultants.com/