Recommendations for a fast (GHz) scope ?

[G0HZU]

Didn't you just state that a 4GHz TDS7404 would be a good choice for UWB development even though there's absolutely nothing special on that scope aside from the fact that you read about it in some papers?

I offered it as a performance benchmark to compare against newer scopes (budget permitting). i.e. as an old scope that has been used for UWB research work that had the BW the OP desired and was within the budget limit. I'm pretty sure this is the model we have at work. We have newer and better scopes but these aren't worth mentioning as they are beyond the OPs budget.

[G0HZU]

OP, not sure what requirements you have.   I would be interested in hearing more about what processing you would need to do for this application.

Agreed. I assumed the OP would just use the scope for single shot or low PRF applications to do some verification etc. The Tek TDS7404 offers 20GHz sample rate on single shot or single channel.

I dug out an old paper on UWB pulsed radar that used this scope and they achieved a 50ps timeslot with this scope. This is directly related to the 20GHz sample rate on a single channel. Presumably this rate offers a decent range resolution. This performance is pretty good although this old school scope obviously uses interleaved ADCs to get this high sample rate. The processing was done externally in this case.

The TDS7404 was useful for stuff like this because it offers this fast timeslot that gives good range resolution. But I'm beginning to feel like I shouldn't have bothered mentioning the TDS7404 as a benchmark 

I'm not familiar with the LeCroy scopes so I'll leave it to Wuerstchenhund to show the single shot performance and  timeslot (and therefore range resolution?) the LeCroy model(s) can expect to achieve for a similar cost budget.

[LeoUCDavis]

Wow I'm surprised by this many responses. Thank you all. Seems to be a good amount of stuff for me to study ...

I'm in the US btw.

[LeoUCDavis]

Are probes included in budget?   Probes can add up depending on what you need.

No we normally just use RF cables.

[Wuerstchenhund]

I dug out an old paper on UWB pulsed radar that used this scope and they achieved a 50ps timeslot with this scope. This is directly related to the 20GHz sample rate on a single channel. Presumably this rate offers a decent range resolution. This performance is pretty good although this old school scope obviously uses interleaved ADCs to get this high sample rate. The processing was done externally in this case.

Yes, 50ps because as you say that is the timeslot resolution of the TD7404.

I'm not familiar with the LeCroy scopes so I'll leave it to Wuerstchenhund to show the single shot performance and  timeslot (and therefore range resolution?) the LeCroy model(s) can expect to achieve for a similar cost budget.

I couldn't be bothered to check for the WaveMaster but even my 3GHz WavePro 7300A can do timeslots down to 20ps 50ps and that on two channels simultaneously.

Also, the higher Time Interval Accuracy (+0.15/Sample Rate + (10 ppm * Reading) for the TDS7404, <0.06/Sample Rate + (10 ppm * Reading) for the LeCroy), Sample Rate and Delay Time Accuracy (±10 ppm for the Tek vs ±5ppm for the WavePro) and lower Trigger jitter (7ps TDS7404, 2.5ps WavePro) certainly helps. As does being able to do a lot of the processing on the scope directly.

All for approx $5k.

Although I admit that the comparison isn't really fair. The TDS7404 is a pretty old-fashioned scope, and the successor DPO7000 would actually be closer to the WavePro's/WaveMaster's performance class. However I haven't seen one going for less than $10k, not even the 500MHz models.


Edit: apologies, I was a bit in a hurry and picked up the wrong time slot, which of course is 50ps for the WP7kA as well (1/20 GSa/s.)

[G0HZU]

Just to clarify, I'm referring to the time interval at the real time sampling limit of the scope. So are you saying the $5k used Lecroy can sample at 50GHz on one channel (and in single slot) in real time to get that 20ps?

I'm not familiar with the LeCroy range so I don't know the age/cost/specs of them because they all have similar names.

I also don't know that much about UWB radar but it's usually used for short range high resolution operation and I assumed that the scope would be used to sample a channel at 20GHz and store maybe 5000 samples and then export this for processing. Then step and repeat for each Tx pulse.

Normally, in a radar range equation, the range resolution is a function of the real time sampling rate because the sampling sets the range bin size. So what real time sampling rate can the LeCroy deliver on a single channel and in single shot mode?

[Wuerstchenhund]

Just to clarify, I'm referring to the time interval at the real time sampling limit of the scope. So are you saying the $5k used Lecroy can sample at 50GHz on one channel (and in single slot) in real time to get that 20ps?

No. I just didn't pay attention as I was in a hurry and picked the wrong figure  while my mind was somewhere else 50ps it is for the WavePro of course. Apologies for the confusion.

So what real time sampling rate can the LeCroy deliver on a single channel and in single shot mode?

20GSa/s in single and dual channel mode, 10GSa/s in triple and quad channel mode.

[G0HZU]

It would be interesting and helpful to hear some system info from the OP what the sampling and range requirements are. It could be that the requirements demand a modern scope with a better sampling system. Or the opposite could be true.

My interpretation of the scope requirements are really basic. I would see it as little more than an ADC in a big box that takes maybe 5000 samples after each Tx pulse and sends this small packet of info to an external processing system. Because the pulse repetition frequency is probably going to be quite low (just a few kHz?) then the overall data transfer should be easy. But this is just my interpretation of a basic concept demonstrator system.

I think the upper limit of the old TDS7404 is 400,000 triggers (or radar Tx pulses?) a second but I'd expect that a typical dev system wouldn't operate a PRF this fast.

So I'm not sure that the slow old UI and other aspects of the (very dated) TDS7404 will matter that much. Obviously, if it was used for other tasks it would be a bit of a dog compared to a modern scope.

I think our 7404 at work is mainly a dust collector these days because the engineers reach for the faster/better/£££ modern stuff instead. I've seen it in use and it was very big and made lots of fan noise so it was not popular in the labs with anyone sitting nearby

Someone mentioned hiring a scope and maybe this would be a wise thing to do even if it just meant hiring a one of the >10 year old scopes like the TDS7404 or LeCroy models for a week.

I'd be tempted to also blag a brand new £££ modern scope on trial/approval/demo and see what things the older scope can't do.

[Wuerstchenhund]

It would be interesting and helpful to hear some system info from the OP what the sampling and range requirements are. It could be that the requirements demand a modern scope with a better sampling system. Or the opposite could be true.

Indeed. It may well be that even a lower bandwidth scope does fine. Without getting some more details from the OP this really boils down to "some 3GHz+ scope for <$7k".

[G0HZU]

Hi Joe
I found the single shot sample rate info vs model type on a google search so I deleted my question above as you were probably typing your answer!
Sorry for any confusion caused...

 

[Wuerstchenhund]

Nothing from the OP on what they need other than >3GHz? 

It looks like we won't hear much more from the OP.

[rfbroadband]

go with the R&S RTO series or the Keysight S-Series.

The RTO has the best hardware based FFT in any scope on the market, you get a low end usable spectrum analyzer for free.

The S  series scope has lower jitter than the RTO, but FFT is software based and rather slow.

[Wuerstchenhund]

go with the R&S RTO series or the Keysight S-Series.

You're joking, right? A basic 600MHz RTO starts at roughly $14k, and the 4GHz variant starts at $37k:
http://shop.rohde-schwarz.com/us/test-measurement/oscilloscopes/oscilloscopes.html

The Keysight DSO-S is in the same ballpark ($17k for the 500MHz variant, $37k for the 4GHz version):
http://www.keysight.com/en/pd-2396122-pn-DSOS054A/high-definition-oscilloscope-500-mhz-4-analog-channels?nid=-32877.1087978&cc=US&lc=eng
http://www.keysight.com/en/pd-2396465-pn-DSOS404A/high-definition-oscilloscope-4-ghz-4-analog-channels?nid=-32877.1087982&cc=US&lc=eng

So how do these scopes fit into the OP's budget of $7k then?

The RTO has the best hardware based FFT in any scope on the market, you get a low end usable spectrum analyzer for free.

It's true that FFT is pretty fast on the RTO (and that it's faster than on the Keysight DSO-S), but it still leaves you with the narrow (up to 4GHz, as that's the top end R&S offers) bandwidth of the scope, and it's no replacement for a proper spectrum analyzer. The RTO are good scopes (and it's nice that there is an OCXO option available for them) but for what they offer they are quite expensive (as are the options, accessories and R&S support), they offers limited analysis capabilities (and most of them are aimed at the telecoms market) and have a pretty convoluted UI. Price-wise it's also very close to LeCroy WavePro 7zi(-A), which is a 40GSa/s high end scope with tons of advanced analysis options.

However, all that is pretty irrelevant considering that the $7k of the OP will neither buy him a R&S RTO nor a Keysight DSO-S.