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Frequency Divider for older Oscilloscopes??

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bdunham7:

--- Quote from: tggzzz on July 19, 2021, 03:08:13 pm ---
No, I wouldn't send  you packing. Nothing special about the term "observe", use "see", "visualise", "measure" etc. Yes, all the energy does lie within those bounds; that's the key point :)

True if the signal is repetitive, but for a non-repetitive signal you have to capture it all on the fly (i.e. realtime).

--- End quote ---

I'm thinking 'observe' might refer to seeing some or all of the characteristics of the signal.  If the energy is truly confined to that bandwidth and you want to capture it sufficiently so as to be able to determine all of the remaining characteristics, I think you need at least 20MSa/s plus at least a small margin to make it practical.  But just a 20MSa/s sampling system isn't all you need--the other stuff necessary would not be trivial, at least for me.

tggzzz:

--- Quote from: bdunham7 on July 19, 2021, 03:26:43 pm ---
--- Quote from: tggzzz on July 19, 2021, 03:08:13 pm ---
No, I wouldn't send  you packing. Nothing special about the term "observe", use "see", "visualise", "measure" etc. Yes, all the energy does lie within those bounds; that's the key point :)

True if the signal is repetitive, but for a non-repetitive signal you have to capture it all on the fly (i.e. realtime).

--- End quote ---

I'm thinking 'observe' might refer to seeing some or all of the characteristics of the signal.  If the energy is truly confined to that bandwidth and you want to capture it sufficiently so as to be able to determine all of the remaining characteristics, I think you need at least 20MSa/s plus at least a small margin to make it practical.  But just a 20MSa/s sampling system isn't all you need--the other stuff necessary would not be trivial, at least for me.

--- End quote ---

You've got it!

And yes, the sampling aperture does need to be <<1ns, but that is a very small part of the circuit: a pulse, a sampling diode, and a capacitor. High speed scopes typically have nothing else at the front end, and are rather fragile - just like spectrum analysers.

Having said that, one of the few significant advances recently has been the stunning improvement in ADCs and DACs speed and resolution, thus making sampling bridge front ends less important than they were.

Jorge Ginsberg:

--- Quote --- The Infiniim XUR series starts at 5GHz and goes to 110GHz albeit with only a 5bin ENOB. I can't afford one.
--- End quote ---

Opsss.. I must admit that I did not know him.
I am now in my 74's, I am retired, and I have not worked in any laboratory for more than 15 years.
I must admit that I have become somewhat out of date.
That's called "old age"....haha....
I guess that in 500 years the waves will be drawn in the air....  :-DD  :-DD

David Hess:

--- Quote from: tggzzz on July 19, 2021, 03:49:04 pm ---And yes, the sampling aperture does need to be <<1ns, but that is a very small part of the circuit: a pulse, a sampling diode, and a capacitor. High speed scopes typically have nothing else at the front end, and are rather fragile - just like spectrum analysers.
--- End quote ---

The sampler is a small part of the circuit but more than just a fast sample and hold because the gate time is much shorter than the settling time.  The schematic may show a switch followed by a capacitor but a lot more is going on and in practice the capacitance is actually a transmission line.

Modern high speed oscilloscopes are nothing like this and have a linear front end using exotic MMIC technology so closer to a traditional DSO except for the weird mixing and interleaving ones from LeCroy and Keysight.


--- Quote ---Having said that, one of the few significant advances recently has been the stunning improvement in ADCs and DACs speed and resolution, thus making sampling bridge front ends less important than they were.
--- End quote ---

Modern ADCs are amazing.

tggzzz:
Radio stops, by definition at 300GHz and IR begins.

Even at 60GHz a high gain ceramic antenna can be improved by adding a 1/4 wave anti reflection coating, just like an optical lens.

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