Pocket-Sized 6 GHz 1 TS/s ET Scope

[SJL-Instruments]

Hope this is allowed here - we'll keep it brief.

We're a small US company that has developed a series of 6 GHz USB sampling oscilloscopes.
Our main goal is to offer access to the picosecond regime (>= 1TS/s ET) at a competitive price (~$2k USD $1500 with hobbyist discount).

Headline features:
- 1 ps time resolution (1 TS/s ET sampling.) Most units achieve ~0.3 ps reproducibly.
- 12-bit vertical resolution, 40 ps rise time
- Edge trigger on channel (rising/falling edge with adjustable level, full bandwidth).
- Pocket-sized, powered over USB C. About the size and weight of a phone.
- Excellent build quality - body is machined aluminum 6061. We are right-to-repair friendly.
- Large portion of manufacturing done in-house (USA) - board-level assembly, laser engraving, even the packaging!

We understand this is a very niche instrument - but we hope we struck a good balance of price and capability within this niche. Curious to hear your feedback (good or bad)!

***
Update 2024-02-18: joeqsmith has now published a quite thorough review of the 4-channel model. You can watch it below:

***
Update 2024-02-28: Shahriar (The Signal Path) has now published his review:

[nctnico]

Any datasheet available?
How many channels does it have? What is the trigger jitter like? What is the realtime samplerate?

[SJL-Instruments]

Section 1 of the User Manual has all the specs you'd find in a datasheet: https://www.sjl-instruments.com/user-manual.pdf

2-, 4- and 8- channel models are available. (The 8-channel model has a 4-6 week lead time, others ship for free next business day.)

Intrinsic trigger jitter is ~4 ps. Due to the RMS jitter of the delay generator, the effective trigger jitter increases with sqrt(T). User manual Section 2.3 has the formula.
(See also the upper right plot on the calibration sheet: https://www.sjl-instruments.com/sample-calibration.pdf)

Realtime trigger rate is 25 Mtrig/s. This is limited only by the minimum holdoff (40 ns). Note that this is not equivalent to the "sample rate," as the scope uses a rather unique architecture (see Section 2.1 of User Manual).

[TheSteve]

Please consider sending one to Shahriar at TheSignalPath if he is willing to perform a review.

[SJL-Instruments]

Yep, we already sent one to Shahriar 
Understandably, he has a long backlog to get through, so the video may not be out for a while.

[azonenberg]

Oooooh you're directly measuring the CDF not the PDF?

Sounds like you built the concept I tossed over years ago called FREESAMPLE (as in "free/open source sampling scope").  I have an incomplete design https://github.com/azonenberg/freesample if you're curious but realized I didn't know enough about high speed design at the time and tabled it. I had successfully prototyped the concept at 10 Gsps in a PMOD hanging off a Xilinx FPGA but never took it to its logical conclusion so I'm happy someone else is exploring the technology.

Your docs are light about internal details and I understand if you don't want to share all your secrets yet but here's my crack at theory of operation based on how my design worked: Variable delay line after trigger comparator (my design had a CDR PLL option as well, not sure if you have that... looks not?) driving the latch port of a high speed latching comparator fed by the signal. At the time I did my design the best option was the Hittite (now ADI) HMC674/675 which had around 10 GHz analog BW. Other input of the comparator driven by a DAC (12 bits in your case).

Each trigger collects one bit of data: the input was or was not greater than Vdac at time offset T.

Repeat a large number of times and divide by the number of triggers to get the probability of the signal being less than Vdac at time T, then sweep Vdac and T across the display range to measure the CDF of the signal.

Partial derivative of CDF with respect to dV then gives the PDF, aka intensity graded waveform.

EDIT: Not sure how your capture system works. The advantage of my architecture was that if you went with the PLL based sampler rather than the delay line sampler you'd get multiple samples per trigger at the PLL output frequency (which could be divided down a lot from your symbol rate, say one sample per 8 UIs or something). You could then capture this with an FPGA input at fairly high rates. I forget the details but I think I was aiming for circa 1 Gsps realtime (1 bit) sample rate using a 7 series ISERDESE2. This approach also avoids jitter getting too high due to excessive analog delay (since you can delay by fractional or integer PLL cycles to get arbitrarily long delays) and allows arbitrarily deep memory.

Am I pretty close?

[SJL-Instruments]

Pretty close, yes! Attached is a picture of the RF side of the board if you'd like to take a stab at it.

The general idea has been floating around for a while (e.g. the Tektronix BERTScope). The hard part is the sub-ps timebase precision (months of aging trials, and calibration takes several hours per device). Achieving an accurate, full-bandwidth edge trigger isn't trivial either.

(By the way, internally everything is 16-bit. Since the ENOB is only ~8.5 at 100 MHz, though, it seemed disingenuous to advertise a 16-bit scope.)

No CDR PLL at the moment - we may offer an external one in the future. You can make a "pseudo-eye-diagram" with just an edge trigger, though.

Re: your edit. We tried this, but it turns out to not save much time in practice (since the samples you want are spaced much more densely than 1 ns).

[coromonadalix]

Is it me,  but seem very poor on input parts protection, impedance ??


ah some similarities against the picoscope  gui   i hope it is configurable, and  not blocked to the "dark" theme,   some colors are almost unreadable

[SJL-Instruments]

Yes, the inputs are ESD-sensitive - this is mentioned in the manual. It's hard to do ESD protection at these frequencies without affecting performance.
(If you do blow up an input, though, it's a free warranty repair.)

Thanks for the feedback on the GUI. We'll add a light theme and check all the text against accessibility guidelines.

[azonenberg]

Let's see, I see a Spartan-7 FPGA, Tag-Connect JTAG connector, USB-C port, and a bunch of QFNs that aren't in focus enough to read part numbers. The SMAs look to be edge launch but with through-board ground/mechanical pins similar to Amphenol RF 901-10510-2 but not that exact part.

The IC next to each input is probably the comparator, and the one near the center of the board is probably a 1:4 buffer to send the sampling clock out to each one.

The leftmost port has some extra circuitry that seems to connect back to the clocking structure so it's probably the only one that can be used as a trigger. First chip behind the comparator is probably a 1:2 buffer sending one leg to the FPGA and one to the delay line for the clock.

Then another buffer or mux or something, with one leg going to the FPGA and the other to the main clocking system. The TSSOP also looks like it might be a 2:1 mux (selecting either the undelayed or delayed clock perhaps?) and the ON SEMI chip might be the actual delay line. Whatever it is, it has ECL/PECL outputs (load resistors to ground plane right at source, then differential terminator at the sink side by the TSSOP). I can't read the full part number but the pinout and package are consistent with the MC100EP195 which has ECL outputs.

Definitely a more cost optimized architecture than my "no holds barred" design which called for a LMK04806 PLL and a HMC856 delay line after it for fine phase shifting. That delay line alone is probably as expensive as your whole BOM.

[azonenberg]

As far as protection goes there are some pretty low capacitance ESD diodes you might want to look at that would be better than nothing, SZESD7471N2T5G claims 350 fF for the diode itself (assuming you do a good layout and probably cut away some ground plane to avoid adding excess capacitance that way). I'm considering that for some upcoming designs that will run up to 10 Gbps.

[JohnG]

350 fF is -j76 ohms at 6 GHz. If the design was 6 GHz without protection, it will be closer to 5 GHz with protection, not counting any stray inductance. That's a substantial hit.

John

[JohnG]

Speaking of bandwidth, any chance there is something higher bandwidth in the works? Asking for a friend

John

[SJL-Instruments]

@John - We don't want to say much about that at the moment  What bandwidth did you have in mind?
Note that the 0.35/tau bandwidth for the GigaWave is usually around 10 GHz. (The datasheet "typical" 8 GHz is conservative.) The advertised 6 GHz is very conservative. Since the response is not quite Gaussian, the effective number depends on your application.

[mawyatt]

Interesting, nice work

This architecture seems like a subset of the Non-Uniform-Sampling (NUS) ADC concepts championed by Dr Mike Chen at USC back in 2000s.

With the NUS ADC the input signal in quantized in both amplitude and time, which offers some unique features/characteristics (like post Anti-Aliasing filtering) as shown in the references below.



https://ieeexplore.ieee.org/abstract/document/6503693

Here's a low resolution image we took long ago of an early developmental Non-Uniform Sampling ADC chip fabricated in 65nm TSMC CMOS.

Best,

[KE5FX]

Nifty.  Seems like a natural for TDR applications, especially if additional input protection is provided in a later model.  Any plans for a built-in stimulus source?

[SJL-Instruments]

@KE5FX Thanks!

A standalone TDR device is on the map. The architecture can be significantly simplified since you control the trigger source. Probably $1k-2k for a few-channel device.

We have limited resources, though, so our focus for now is customer/software support for the GigaWave. Our guess is that there's a broader audience for scopes than TDR. (We could be wrong, though!)

For an external stimulus source, Leo Bodnar's pulser gives essentially optimal performance per dollar.

[JohnG]

@John - We don't want to say much about that at the moment  What bandwidth did you have in mind?
Note that the 0.35/tau bandwidth for the GigaWave is usually around 10 GHz. (The datasheet "typical" 8 GHz is conservative.) The advertised 6 GHz is very conservative. Since the response is not quite Gaussian, the effective number depends on your application.

Got me, I don't really have a sound idea, other than substantially more than 6 GHz - at least 2x and probably 3x or more. I have been looking at using TDR in order to learn about and then implement better transitions for connectors (mostly SMA and MMCX), as well as improving some probing points on some of my designs. These are basically transmission line probes built into a PCB. They work surprisingly well, but I'm starting to see some higher frequency junk (at least 5-6 GHz) and I don't have a good idea how real it is and if I need to do or can do anything about it.

The circuits are power pulse circuits, so there are also resonances in the feed networks and the impedances are low due to the high currents required. I'd also like to use TDR here to see if it can help me locate problem areas with less guesswork.

It's hard for me to justify expensive equipment to my company for this because I don't know enough about this topic, and the circuits fall well outside of the usual signal-level stuff. I have a budget 6 GHz VNA now, and a decent, if rather old, 6 GHz real-time scope (SDA 6020), and it's not enough. A relatively affordable way to get to something higher BW might withstand budgetary scrutiny.

Sorry for the vague answer, but this is new territory for me.

John

[points2]

Hi,
I saw your post just after you posted... I jumped on your web site...
nice ! 

We understand this is a very niche instrument

A sampling scope from A-brand @ A-brand price is a nice market, for sure !
But at 2-3kEur, it can be a dedicated instrument, a "dead-cheap" alternative to high-end benchtop (high BW, high sampling rate).
(I think... I admit I'm a noob compared to the experts that posted earlier  )

- but we hope we struck a good balance of price and capability within this niche. Curious to hear your feedback (good or bad)!

Do you plan to release a video (youtube ...) to demo the device & see how it behaves ?

[joeqsmith]

Yep, we already sent one to Shahriar 
Understandably, he has a long backlog to get through, so the video may not be out for a while.

Look forward to seeing it.

[SJL-Instruments]

@points2 re: the video. Yep, something basic (unbox, measure a few signals, eye diagram) is in the works.
Of course, Shahriar's review will be 30 dB better in quality than anything we can make. (And more importantly, unaffiliated.)

[points2]

Hi,

@points2 re: the video. Yep, something basic (unbox, measure a few signals, eye diagram) is in the works.

"basic" !?
Your product has not the price tag of a tinySA / LiteVNA / tinyPFA / etc.. I bought 2 items of each without headache vs the expenses.
Your product is not a 100Eur device, it is 3k (VAT incl.) ; thus not the kind of device any hobbyist pays to check how it works and how it performs.
1ST => be customer oriented : do as many videos as you can to explain the device / perfs / capabilities...  a basic unboxing & playing fast with the device in a few min video worths nothing.
The picoscope 9402-05 is the match. x4 more expensive, ok, but capabilities are quite ok.
In this niche market, please do explain how this x4 ratio in price, is 1:1 in some measurements or 1:2 in some other measurements... etc..

Of course, Shahriar's review will be 30 dB better in quality than anything we can make. (And more importantly, unaffiliated.)

you said earlier : Shahriar's review is queuing... and we reveiw is expected in "a while"
Speed up the process and send your product to any guys (many experts, with many posts & high reliability) in this forum. Pretty sure sure they will do a far better review than Shahriar, because quick & relevant vs the potential of your device for hobbyist.
Don't get me wrong, Shahriar reviews are 1st-class... but it's all about "pro" stuff @ price tag way above the hobbyist budget (see its last videos) ; but any hobyist can learn form him, and that's ok.
All  the best 

[joeqsmith]

... thus not the kind of device any hobbyist pays to check how it works and how it performs.
1ST => be customer oriented : do as many videos as you can to explain the device / perfs / capabilities...  a basic unboxing & playing fast with the device in a few min video worths nothing.  ...
....
Don't get me wrong, Shahriar reviews are 1st-class... but it's all about "pro" stuff @ price tag way above the hobbyist budget (see its last videos) ...

Tend to agree with above statements.  I think if I were wanting to compare it, it would be with something like the iC227 below.

I still use my old sampling scope to look at ignition waveforms.  Sure, it's 40 years old but it's well made and able to handle a pretty tough environment.  Making these measurements with the OPs product may pose a unique problem as they chose USB for an interface.   In my experience, that bus is prone to failure in high noise environments, such as looking at ignition sources. 

The iC227 is an 11GHz bandwidth Sequential Sampling Oscilloscope. Our Price: $3,762.75
https://us-shop.ichaus.com/mobile/Product.aspx?ProductCode=iC227_Dual_11GHz-_Oscilloscope

[SJL-Instruments]

Points taken. To start, we now have an outline for ~8 detailed videos on specific topics with demos. We'll spend the next week planning these in more detail and hopefully starting production.
In full honesty, we cannot promise a fixed timeframe for this, but we understand if you want to withhold purchasing until they're out.

Re: The iC227. We do not have this device, but from the datasheet:
1. The timing precision of the iC227 is 0.5% FS (5000 ppm), vs 15 ppm typical for the GigaWave.

2. The timebase of the iC227 is calibrated and stored in a LUT.
For the GigaWave, we have developed a quite detailed model of the timing of the delay chip that is robust against temperature variation and year-scale aging. We calibrate the dominant parameters in the model once at the time of manufacture (this is the several-hour part), and perform a fast recalibration at each sampled delay during use. The precision is reliably 2 ps RMS @ 20 ns without the fast recalibration step, and ~0.2 ps RMS with this step.
We can only speculate on the iC227, but we would be very surprised if a LUT held better than 10 ps precision over an hour (or if the device is bumped). (The claimed 1 ps is believable immediately after calibration.)

3. The GigaWave is capable of intensity grading (e.g. eye diagrams and modulated signals).

4. (Subjective) We would argue that our software is easier to use (you can drag channel/trigger markers vertically, and scroll/pinch to zoom timebase and vdiv). We have more measurements, FFT, and data export. We are also actively implementing feature requests.

5. We could not find anything like the iC227 with more than 2 channels.

We hope this addressed your concerns. Thanks again for your feedback and steering us in the right direction.

[joeqsmith]

I have downloaded and installed your software for Windows.  Is there an interface tool kit that will allow me to run it using my own software?  For example, say I want to use it as part of some automated test. 

Looking at the manual and software, it appears that the export feature only saves the data that is currently on the screen.  It also appears that it does not allow all of the traces to be saved to a single file.  Can you confirm? 

The software seems very easy to drive.   When I look at the demo mode, I can see the trigger level marker on the plot but I don't see a time marker.   If I pan to the left, it seems to not show data at time 0, but rather 11ns.  Rather than having all the data on a single graph, why not allow more options? 

3. The GigaWave is capable of intensity grading (e.g. eye diagrams and modulated signals).

I could not figure out how to setup a mask.  Is that not supported?

Looking at the manual, I noticed the following comment:

The main limitation of the GigaWave™ architecture is for signals with infrequent trigger opportunities (500 ktrig/second or lower).

A typical ignition system for example would be less than a kHz.  I have a very old Tektronix pulse generator head that will produce a <25ps edge.  The pulse period is about 120kHz.