4 GS/s Oscilloscope with averaging and VERY fast retrigger. - Page 1
Forum section: electronics / testgear

author: ezalys
author_rank: Frequent Contributor
timestamp: March 08, 2020, 06:54:35 am
content: Dear all,I'm working on an experiment which measures the response of a system to a 2-10 us long pulse sequence. The response is very deep in the noise and requires a lot of averaging of the response signal. The system recovers instantaneously after the pulse sequence, and thus we would like to repeat the pulse sequence as soon as possible. I'm struggling to find a signal averaging oscilloscope that's able to respond faster than 1 microsecond (FastFlight-2 signal averaging oscilloscope, not available anymore) after the end of a trace. We can't miss triggers, as a missed trigger means missed data, missed averages, and therefore longer to collect enough averages to obtain meaningful data. Does anyone have an idea for how to average a million or so repetitive segments of analog signal without losing data?Best,E

author: tautech
author_rank: Super Contributor
timestamp: March 08, 2020, 07:19:46 am
content: I can't help thinking a modern deep memory DSO in slow timebase Roll mode and using History and a good trigger suite will provide what you're looking for.How many channels do you need to use at the same time as this might have a negative effect on the sampling rate if 2 or more are used on the same ADC.

author: nfmax
author_rank: Super Contributor
timestamp: March 08, 2020, 08:59:44 am
content: The higher-specced Keysight MegaZoom 4 scopes, like the DSO-X 3104T or the 4000X series, advertise a waveform update rate of over 1 millison waveforms/sec, and claim to be the industry's fastest. I suggest you take a look, and/or call your local Keysight office.

author: tautech
author_rank: Super Contributor
timestamp: March 08, 2020, 09:25:57 am
content: I dunno, pick your poison, slow timebase setting and deep memory = zero rearm timeorXn wfm/s with some blind time.

author: gf
author_rank: Super Contributor
timestamp: March 08, 2020, 09:33:35 am
content: Quote from: ezalys on March 08, 2020, 06:54:35 amIs it really important not to lose any cycles if the signal is periodic anyway?[ And if it is not periodic, what's the sense of averaging, then? ]Do you need "real-time" display, or might it be an option to capture just one or multiple huge buffers of samples, and align and average them offline (e.g. with Matlab, Octave or whatsoever).If the required sampling rate is lower than the highest sampling rate of the digitizer, "Hi-Res" acquisition mode may help additionally, in order to improve SNR.

author: nfmax
author_rank: Super Contributor
timestamp: March 08, 2020, 10:43:32 am
content: Quote from: nfmax on March 08, 2020, 08:59:44 amOne minor problem - you are limited to 65536 averages in average acquisition mode. But maybe you could do 16 'blocks' of 65536 averages, with a longer gap between each block, using segmented memory mode, (or possibly you will have to retrieve each waveform buffer over the LAN, depending on how the average & segment acquisition modes interact). Then average each acquisition together separately.I spent almost 20 years involved making systems that do just this sort of averaging: but we always used custom hardware, which progressed from a board full of logic chips & fast RAMs to a single, mid-range FPGA.

author: nctnico
author_rank: Super Contributor
timestamp: March 08, 2020, 11:58:17 am
content: Quote from: ezalys on March 08, 2020, 06:54:35 amI'd start with a 10 bit (or more) oscilloscope which can do fast segmented recording and then do the averaging on a PC. I think you probably find something in Lecroy's or R&S (RTA4000 for example) line-up. Doing the averaging on the oscilloscope itself is likely not going to work well due to not using enough bits to do the calculations to a level where you get meaningful data. But you can try; at least the RTA4000 has the ability to show an average of all recorded segments.I don't think you will want to record a million segments though. At some point you start looking at the noise induced by the trigger and sampling system anyway.

author: DaJMasta
author_rank: Super Contributor
timestamp: March 08, 2020, 03:05:31 pm
content: Why do this with just a scope? What is your input frequency/bandwidth? Rather than averaging like crazy to try and see the signal, pick a proper high dynamic range instrument or something with good out-of-band rejection and get a high resolution digitizer in there. Either that or use a preamp and just look at the pulses with a normal scope.

author: nfmax
author_rank: Super Contributor
timestamp: March 08, 2020, 03:28:03 pm
content: Quote from: nctnico on March 08, 2020, 11:58:17 amIf the signal of interest is buried deep in the noise more ADC bits don't help, 8 is more than enough. Also, since the noise spreads the signal over many different bit transitions, the ADC effective DNL is much improved. Furthermore, I would sincerely hope that any decent scope has a wide enough acquisition memory to accommodate the maximum ADC sample summed over the maximum supported number of averages (24 bits, in the case of the Keysight scopes)!The scope must be capable of doing the averaging itself, otherwise you are going to spend most of your time reading out the trace data for each pulse. Doing this once every 65536 pulses is much less of an issue.Trigger uncertainty shouldn't be an issue, as you will be triggering from the circuit generating the stimulus, not the response. Sample jitter and clock drift also don't matter much, if the length of each response is fairly short: although the Keysight scopes I mention have high precision timebase anyway..

author: ezalys
author_rank: Frequent Contributor
timestamp: March 08, 2020, 03:38:19 pm
content: DaJMasta - We use a preamp cooled to four kelvin already and the data is still this noisy. The 1/f knee is a real bear.nctnico - We do see trigger noise and we average it out.

author: DaJMasta
author_rank: Super Contributor
timestamp: March 08, 2020, 03:51:31 pm
content: That's probably about as much as you can expect out of a preamp then.... have you looked into PXI or similar high speed digitizers? You can find models to 100MS/s and 14 or 16 bits for not too much money, though you need the chassis/controller (unless you go with a PCIe based one or something) - while they may not boast a high retrigger rate, if you have that much resolution, you may not need much averaging to be able to discern your signal. If they're based off PCIe (or PXIe), then they may actually have enough bandwidth to run the sample rate you require without having to retrigger at all, just dumping to memory or a fast SSD.Another option could be a spectrum analyzer with realtime analysis capability. If you had 20MHz+ of instantaneous bandwidth, you could park the center frequency at like 10MHz and just directly digitize the input without sweeping, which gets you probably 14 bits of resolution with a much lower instrument noise floor.Since your bandwidth requirement sounds low, slower, higher resolution digitizers are probably an option. I assume you are already, but if not, bandpass filtering around your frequencies of interest could do a fair bit for system noise floor too!

author: Marco
author_rank: Super Contributor
timestamp: March 08, 2020, 04:25:53 pm
content: 500 kHz retriggering signal averaging, 4 GS/s sample rate :https://www.engineersonline.nl/download/U1084AEN.pdf

author: nfmax
author_rank: Super Contributor
timestamp: March 08, 2020, 04:31:30 pm
content: Quote from: Marco on March 08, 2020, 04:25:53 pmAnd built-in averaging firmware as well - nice! This is the sort of hardware averager design I've been involved with over the years.

author: JDubU
author_rank: Frequent Contributor
timestamp: March 08, 2020, 04:43:18 pm
content: Don't know if this is helpful, but the new low end Keysight 1200x series advertises a 1uS trigger re-arm time in segmented memory mode. Maximum number of segments is only 500 though.The higher end Keysight InfiniiVision scopes have the same re-arm time but up to 1000 segments.https://www.keysight.com/main/redirector.jspx?action=ref&nid=-32110.0.00&lc=eng&cc=US&ckey=3035376&cname=EDITORIAL&nfr=-32110.1286929

author: ezalys
author_rank: Frequent Contributor
timestamp: March 08, 2020, 05:26:35 pm
content: Marco - Looks like Bruker uses these in their mass specs. Very similar requirements to what we do... very promising.DaJMasta - The bandwidth requirement is very high. We need about 1 GHz of bandwidth going down to DC, hence the 4 GS/s in the title. We have a setup that works using the FastFlight-2 system, but it's no longer made.

author: Someone
author_rank: Super Contributor
timestamp: March 09, 2020, 01:05:44 am
content: Quote from: ezalys on March 08, 2020, 05:26:35 pmDo be careful with the term "averaging", that U1084A-AVG linked accumulates all the acquisitions equally. On the other hand while many oscilloscopes have an "average" acquisition mode, its typically a weighted average (IIR type response) and not a true boxcar. Some Lecroy models offer both a pre-processing (IIR) and post processing (accumulation) averaging option.That said a high waveform rate even with the less effective IIR averaging can still be more powerful for filtering noise in a given time. And can be combined with accumulating periodic captures of that.

author: ezalys
author_rank: Frequent Contributor
timestamp: March 09, 2020, 01:18:46 am
content: It's VITAL that this operate in accumulation and not IIR mode.

author: DaJMasta
author_rank: Super Contributor
timestamp: March 09, 2020, 03:35:56 am
content: If you really need 1GHz bandwidth (not what I expected from reading 2us+ long pulses) and this kind of retriggering... I think you're looking at a fairly high end scope, then.Keysight's MSOS series (or better, the MSOS only specifies 300k+ waveform updates/sec)Rohde & Schwarz's RTM/RTA/RTO 2000 seriesTektronix's MDO4 series or better (the 3 series specifies up to 280k waveform updates/sec, but the 4 series goes to 500k)It sounds like LeCroy's HDO series can only capture that fast in sequence mode, but the WaveRunner HD 8000 series could do it - they specify up to 650k waveform updates a second with no mention of sequence mode onlyNot sure if any of these meet every requirement, but they can update the screen frequently enough to likely meet your requirement, have at least 1GHz bandwidth options available, and are all high resolution (10bit+). They're also all basically current-gen, so be prepared to shell out a bit (though it sounds like a research application, so this is probably less of an issue). And with any case, get a demo to make sure. For this price, it's important to check and be sure.

author: Keysight DanielBogdanoff
author_rank: Unknown
timestamp: March 09, 2020, 03:55:38 am
content: You also might look into the Keysight 6000 X-Series scope (D/MSOX6004A). It's the highest-end InfiniiVision scope, and goes from 1 GHz to 6 GHz (vs. 1.5 GHz max on the others). It uses the same front end as the MSOS mentioned below, which means the noise is quite low. But, it uses the same backend ASIC as the other InfiniiViision scopes(Megazoom IV). It does some fancier analysis stuff too, like color grading, jitter analysis, etc.It goes up to 450,000 waveforms per second (aka triggers). The 3000T and 4000X are also great scopes, will get you double the update rate, and go up to 1.5 GHz.We can definitely get you a demo if you'd like.

author: Berni
author_rank: Super Contributor
timestamp: March 09, 2020, 07:34:21 am
content: I think what you want instead is a deep memory scope.For example the Keysight MSO9000 has 1Gpts of memory so at 4GS/s this gives you 250ms of continuous recording time on one channel. So if you have a event that is 10us long and can repeat it instantly then 25 000 of these events can be captured before the scope runs out of memory and stops. You get a 1GB sized file out of it that you then process with your own software to seek out the events of interest and process them. If you need help identifying where the pulses start you can use another channel on the scope to also capture a trigger signal while still getting 1GPts per capture.But the ultimate device for your task would be a high speed ADC and a FPGA that can continuously sample and process the data in real time. So if you are up to doing FPGA development you might be able to get a existing ADC+FPGA board like for example the RedPitaya.

author: nctnico
author_rank: Super Contributor
timestamp: March 09, 2020, 09:30:25 am
content: Quote from: nfmax on March 08, 2020, 04:31:30 pmThis Keysight U1084A acquisition card seems like it has been designed with the purpose of the OP in mind. It could be a very good solution compared to an oscilloscope. One thing that worries me about using an oscilloscope is that maximum waveform rate of oscilloscopes is only valid for very specific (optimal) conditions which often don't even resemble a normal usage scenario. Averaging may slow it down and the only way to find out is to test the oscilloscope. It also seems that oscilloscope in general don't offer to average over 50k to 100k acquisitions.

author: fcb
author_rank: Super Contributor
timestamp: March 09, 2020, 09:41:29 am
content: Pico Technology 6407 or the newly released 6000 series.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: March 09, 2020, 01:51:22 pm
content: Quote from: ezalys on March 08, 2020, 06:54:35 amSo what is the purpose, i.e. is this to take a snapshot (i.e. a few cycles) or is this for continuous monitoring?Scopes are great for the former but pretty bad for the latter.If you just want to record a number of cycles then I'd suggest you get a scope with very large sample memory. Ignore waveform rates, even the fastest scope will be blind for around 90% of the time so you need a scope that can capture the required sequence in one go. You need to decide how many cycles you want and then multiply with 4GSa/s and then you got the sample memory size you need.I understand that the BW requirement is 1GHz, so yes you want at least 4GSa/s.As to which scopes, forget any of the embedded scopes like the DSO-X, they don't have the memory sizes or capabilities to do what you need. Instead, I would look at the Keysight Infiniium-S DSO-S104. The DSO-S has the advantage of letting you not only select memory size but also sample rate, and it can be optioned up with large memory (536Mpts at<5GSa/s in single-channel mode). I believe it also supports boxcar averaging, and if not it can optionally run MathLab scripts so you can do the averaging there.However, if this is for continuous monitoring then I would just forget bench scopes and look into high speed digitizers, for example as PXI Express system. You can get the raw sample stream from your digitizer and feed it into Mathlab/Octave/SciLab/whatever to get your data.

author: frogg
author_rank: Regular Contributor
timestamp: March 09, 2020, 03:59:52 pm
content: I'm not sure I totally understand your question.A Virtex-7 dev board could easily keep up with your sampling rate. How many bits ADC do you need?The real metric you need to define is cross-sectional bandwidth.The math is pretty simple and could be synthesized with a few blocks in MATLAB.

author: Someone
author_rank: Super Contributor
timestamp: March 10, 2020, 01:19:06 am
content: Quote from: frogg on March 09, 2020, 03:59:52 pmAccumulating is easy in concept, but the OP is asking for an integrated product rather than building something. Scopes have the front end required and triggering performance (critical for the correlation to work) but insufficient offload/processing bandwidth to average as fast as they would like. The U1084A Marco linked to is one of the few products that has everything together in one unit/system.Quote from: ezalys on March 09, 2020, 01:18:46 amIgnore scopes, fastest back-to-back accumulation is going to be something with user programmable logic/FPGA that sees the full sample rate. Pingpong buffers and offload while accumulating the next batch.

author: frogg
author_rank: Regular Contributor
timestamp: March 10, 2020, 01:08:34 pm
content: I'm not sure what you think the differences are between a high speed digitizer with FPGA on-board and a modern FPGA dev board, but uh........ok, mate

author: Marco
author_rank: Super Contributor
timestamp: March 10, 2020, 06:37:30 pm
content: Quote from: frogg on March 10, 2020, 01:08:34 pmOne works out of the box, the other doesn't.What exactly do you have in mind? ADC12J4000EVM + TSW14J10EVM + TEC0330 and some hope and prayer you can make it all work together?

author: nctnico
author_rank: Super Contributor
timestamp: March 10, 2020, 06:40:22 pm
content: Quote from: Marco on March 10, 2020, 06:37:30 pmAgreed. For the OP's purpose the analog front-end design will matter a lot too and there maybe be impedance requirements as well. It is not trivial to get a high frequency signal into an ADC. Besides that getting from the demo applications which come with a dev board to something that is actually useful in a production environment is going to take a serious amount of work.

author: rsjsouza
author_rank: Super Contributor
timestamp: March 10, 2020, 08:19:26 pm
content: Quote from: Marco on March 10, 2020, 06:37:30 pmI love that. Quite on point.

author: moore
author_rank: Contributor
timestamp: March 11, 2020, 01:49:25 am
content: Quote from: ezalys on March 08, 2020, 06:54:35 amWe have a similar acquisition need, mass spectrometry with high rep rate lasers to get high dynamic range after averaging. Gave up on the FastFlights years ago, have tried the Acquiris, they are ok but expensive. Currently using Gage Applied, see product line here:http://www.gage-applied.com/(click tabs for 8 or 12 bit digitizers which have the 4-6Gs/s rates)They have worked hard on minimizing rearm time and keeping data flowing for high rep acquisitions. Also I've been impressed with how their ENOB stays adequate at high bandwidth. They have some ok software for plug n play, but likely you have to use their API and do some programming to get exactly what you want. They do have firmware for fast averaging and other functions.All in all a solid company with good support that seems to be not well known outside the exotic scientific applications community. They are not Keysight or Ametek/Ortec size but they punch above their weight class.

author: frogg
author_rank: Regular Contributor
timestamp: March 11, 2020, 09:04:08 am
content: Quote from: Someone on March 10, 2020, 01:19:06 amHi Someone,I'm sure we are just talking about the same thing. It is extremely common in industry to pair what is essentially an FPGA development board with a high speed digitizer front end. There are usually a few cards or even a single integrated card in some cases that fit into a backplane, like NI FlexRIO. Sometimes the terminology varies by manufacturer, sometimes it's a "development board". Sometimes it's just called a "high speed digitizer."This is extremely common for use in EW and radar systems and high speed optics.The FPGA synthesis toolchain is very simple and easy to use, especially if the necessary logic is straightforward like the OP states.Yes, there is some minor assembly required, but it is really trivial.I don't know what everyone else is talking about (building custom analog front ends is not something anyone suggested and is not written in any post!!)

author: Marco
author_rank: Super Contributor
timestamp: March 11, 2020, 10:37:28 am
content: Quote from: frogg on March 11, 2020, 09:04:08 amThere's high speed and then there's high speed, for their 1 GSPS range Analog Devices has pretty open development boards ... for their 10 GSPS range ADC it's a non reprogrammable black box. TI similarly has non reprogrammable black boxes for appropriate ADCs, though they do give you a FMC+ to FMC adapter so you can use it on FPGA development boards. But that still means a whole lot of DIY and figuring out how to get everything to work together.Teledyne SP and Keysight have digitizers at that speed which allow firmware development, but I doubt that's cheaper than the Acquiris.The Gage Eon Express and Cobramax Express with their averaging firmware do seem an out of the box working alternative.QuoteWell, the TI ADC EVM is AC coupled for instance ... if you want DC coupling you'll have to do some modding.So if the Cobramax Express's 8 bits resolution is enough you can have a working system for 9000$ (website prices, so might be able to negotiate that down). Or you can get 4000$ worth of development boards with a whole lot of DIY hardware and software development. I don't think the saved money is enough to pay for the time spend.

author: ezalys
author_rank: Frequent Contributor
timestamp: March 11, 2020, 11:51:24 pm
content: I'm not paid to develop something or cobble something together. It needs to work now.I've seen these Gage cards and heard very good things. So far it's the gage card vs. the keysight/aquiris. Could you explain a bit more about how they compare?

author: Someone
author_rank: Super Contributor
timestamp: March 12, 2020, 02:01:56 am
content: Quote from: frogg on March 11, 2020, 09:04:08 amYou can keep saying there is some other non-specific way to achieve the solution... but everyone else is providing examples. If you think there are other more appropriate examples, do provide them rather than just saying you know a better way to do it and we don't.

author: moore
author_rank: Contributor
timestamp: March 12, 2020, 04:32:45 pm
content: Quote from: ezalys on March 11, 2020, 11:51:24 pmAquiris hasn't been part of Keysight for a couple of years now. My impression is it was just not a good match. They are a Swiss company. Like a lot of smaller firms, they are looking for the big customer who will develop something around their products and wants to buy 100-1000 eventually. Not to say they won't work with a one-off customer, just be aware they may be focused on a different problem than you are.There's a third option I'd forgotten about - Teledyne SP Devices. I saw them at a trade show. They have cards that seem pretty powerful but are much more than even the Aquiris. I forget if they were PXI only. If a giant company with top level customer support is important though, and money is no object, they may be the only choice of these three.My suggestion is to define your must-need specs, and go through the data sheets of the most appropriate choices at the two/three companies, and get fresh quotes. If they have demo software, get that (GaGe used to). Look at the API documentation. If you have a big budget and lots of time and flexible spec needs, it could be a headache to decide, but then maybe you can get a demo card from each. If you have a modest budget and less time to shop and need to start working, then I'd say go for the GaGe and forget the others.

author: rsjsouza
author_rank: Super Contributor
timestamp: March 12, 2020, 06:52:43 pm
content: Quote from: Someone on March 12, 2020, 02:01:56 amThe only ones I found more or less "ready to run" from the Xilinx page are from Curtiss-Wright. (4GSPS,12GSPSand25GSPS). If they are an aerospace company, purchasing one may be a difficult and costly option.