Pocket-Sized 6 GHz 1 TS/s ET Scope

[SJL-Instruments]

Come to think of it, that would be a mighty fine feature for the software:).

We could certainly do that. The de-embedding calculation itself isn't bad, but the UI requires some thought. The user would need to import s-parameters from a VNA trace.
edit: Implemented as of 2024-01-21.

SLJ, have you considered creating a software interface document for the product that would provide details on how to directly control it?

To clarify, by "it" do you mean the product (i.e. a programming manual for the serial interface), or the software (some way to programmatically control the desktop software)?

[joeqsmith]

SLJ, have you considered creating a software interface document for the product that would provide details on how to directly control it?

To clarify, by "it" do you mean the product (i.e. a programming manual for the serial interface), or the software (some way to programmatically control the desktop software)?

It, meaning your products serial interface.

I have not done the math. I solved my issues well enough by getting a lower loss cable, but in the end I would have preferred to do some de-embedding. Since most de-embedding tools look for s-parameter models of the network to be de-embedding, I imagine that the process involves an FFT to convert the signal to be corrected into the frequency domain, passing it through some sort of inverse of the supplied model, and converting back to the time domain. My math skills are pretty rusty at this point.

Maybe this is an answer: https://github.com/TeledyneLeCroy/SignalIntegrity/wiki

I only skimmed that article I linked but it appeared they suggest at least some scopes allowed you enter the data rather than using s-parameters.   They are using a product made by Teledyne LeCroy. 

The user interface for the cable de-embedding feature requires a description of the cable including its length, propagation velocity, and frequency response. The frequency response can be entered either as the S21 s-parameter forward transfer function as a table or as attenuation per 100 feet as a function of frequency by supplying the constants A1 and A2 from the manufacturer’s frequency response equation.

***
Looking over my coax, I have some RG223 and RG400.  Attached showing a section a bit longer than needed.  It does a fine job filtering that edge.   I wonder with your scope if that 4GHz was based on the length they required for their delay. 

[SJL-Instruments]

It, meaning your products serial interface.

Sure, we'll add a "Serial Interface Programming Guide" section to the user manual (ETA 2 weeks published as of 2024-01-13).
We'll preemptively warn you that the main acquisition commands return dense binary data to minimize communication time. Parsing it is annoying.
We recommend using the Python API, as it's essentially just a wrapper on the serial interface that does this parsing for you.

I only skimmed that article I linked but it appeared they suggest at least some scoped allowed you enter the data rather than using s-parameters.   They are using a product made my Teledyne LeCroy. 

Thanks for this; we'll look into implementing these options.

[joeqsmith]

I have a Signal Hound SA that uses USB 3 that I have written some software for.  When I first looked into it, I remember them having a similar comment, warning that the data is coming in fast and a lot of it.    

Look forward to to see what you come up with for handling the delay line.   I doubt many people would have access to a VNA to measure the S-parameters for their delay line.   Maybe that could be an accessory along with the splitter.   This would give you some control over it. 

***
From the SH manual, time embellishes all:

If you wish to retrieve all samples, it is the responsibility of the users application to poll the samples via fast enough to prevent the circular buffers from filling and eventually having to drop data. We suggest a separate polling thread and synchronized data structure (buffer) for retrieving the samples and using them in your application.

Home made delay line improves the rise time slightly (was 900, now  600ps).  Takes forever to to reach steady state.   Too bad the pre-trigger requirement wasn't more in the order of <1ns. 

[hpw]

Yes, that is the reference timebase (2.5 ppm TCXO).
20-80% risetime is available as a built-in measurement. It is possible to track the long-timescale variation of the risetime, but not the short-timescale fluctuations, since each sweep takes a few seconds.
For 3.3V LVCMOS signals we recommend a 12 dB inline attenuator with x4 probe attenuation in the software.

OK, I understand, so it will not my purchase, as to measure 10Mhz 120dBc @1Hz clock distributions clocks.   

[joeqsmith]

A short article attempting to compare random and sequential sampling:

https://www.apexwaves.com/blog/random-sampling-vs-sequential-sampling/

There is really no meat on the bone.  The summarize with: 

Nevertheless, the advantages of this method in practice outweigh the advantage of the random-sampling method.

, but it you take the time to read the page and a half, they never explain what these advantages are.   They do however explain the short comings.     

This 20+ year old article talks about sequential sampling and where it fits in.   

This capability makes such scopes the instruments of choice in applications of rapidly growing importance-electro-optics, for example.

Of course, they are talking about 50GHz BW, not 6 like the product we are discussing. 
https://www.edn.com/50-ghz-bandwidth-sequential-sampling-dsos-test-10-gbps-network-components/

Outside the scope of this thread, but while searching for articles, I found this set of slides that mentions Teledyne LeCroy's Digital Bandwidth Interleave (DBI).  I made a video that went over this technique based on their patents.   In order to demonstrate how it works, I wrote a simulator for it (starts about 6min in). 

https://keysightevent.com/191023/handout/pdf/c/3.%20Digital%201_High-Speed%20Oscilloscope%20Fundamentals.pdf

[nctnico]

I still don't see why this oscilloscope can only show the part of the signal after the trigger. The 'good old' Tektronix TDS500 series use sequential sampling as well and have no problem showing the signal before and after the trigger point. It seems Tektronix' acquisition system is free-running and timestamping the sample where the trigger occured. After that they phase-shift the sampling clock and take another acquisition.

[SJL-Instruments]

The 'good old' Tektronix TDS500 series use sequential sampling as well and have no problem showing the signal before and after the trigger point. It seems Tektronix' acquisition system is free-running and timestamping the sample where the trigger occured. After that they phase-shift the sampling clock and take another acquisition

We consider "sequential sampling" to refer to any technique where the sampling action is caused by the trigger.
Taking timestamped samples (independent of trigger) and later reconciling with trigger events would fall under random sampling. (See https://w140.com/tekwiki/wiki/Sampling_oscilloscope)
(Phase-shifting a periodic clock as you described is an interesting technique, in some respects a "subsampled version" of RIS.)
Some (very) early Tektronix sequential sampling scopes actually contained an analog delay line - tweaking the compensation network for these was an art.
https://groups.io/g/TekScopes/topic/tektronix_delay_line/7629123

but it you take the time to read the page and a half, they never explain what these advantages are.   They do however explain the short comings.

We tend to agree. In most cases, random sampling provides more flexibility with your trigger setup - but  6 GHz random sampling scope will be 4x the price. Our hope is to provide a lower-cost alternative without compromising on bandwidth. The pretrigger requirement is really the only limitation w.r.t. random sampling (albeit a significant one).

On another note, we have released v2.5.4 of the software containing the promised features for this update. (Except for light mode - next update.)
https://www.sjl-instruments.com/software/

Coax de-embedding is working fairly well (see attached). If you're interested, the math is in "Transient Analysis of Coaxial Cables considering Skin Effect" by Wignington & Nahman.

The UI will just require you to enter cable length and type.
If the type you want isn't available, you can also enter the attenuation data at a few frequencies.
The results still need to be validated further, so it'll be rolled out next update [likely end of next week].

[joeqsmith]

Coax de-embedding is working fairly well (see attached). If you're interested, the math is in "Transient Analysis of Coaxial Cables considering Skin Effect" by Wignington & Nahman.

The UI will just require you to enter cable length and type.
If the type you want isn't available, you can also enter the attenuation data at a few frequencies.
The results still need to be validated further, so it'll be rolled out next update [likely end of next week].

Thanks for the fast turn around on this. 

Does your software also account for the splitter or does it assume it is perfect?   Assuming a 6dB resistive splitter, any advantage to using an attenuator at the scope's trigger input to prevent reflections from perturbing the measurement signal?   If a person did have access to a VNA to fully characterize their setup, any plans to support s-parameters as well?   

[SJL-Instruments]

Compensation for the splitter will come out at the same time as s-parameter import (probably not next update, but the one after implemented 2024-01-21). Coax distortion is dominated by skin effect, and so is quite well characterized by conductor material and geometry (i.e. cable type). Not so with splitters - the imperfections "are what they are," and just need to be measured.

Assuming a 6dB resistive splitter, any advantage to using an attenuator at the scope's trigger input to prevent reflections from perturbing the measurement signal?

Yep, adding a (well-matched) attenuator will reduce reflections, if you can afford the loss in SNR.
This is more important on the delayed signal input (since the coax to the trigger input should be pretty short).

[joeqsmith]

Wasn't sure how good your port match is. 

[points2]

Hi,
This post is from a noob that thought he understood some part of what the device can do... but when joey/ntcnico etc  start posting... I lost again

A few questions at noob level, concerning the use of this "special" device, just to try to get a clearer picture about what it can do :

1. given its limiation due to the way it works => it is a big bargain vs any all-in-one DSO on the market ? correct ?

2. it is a device that works on repetitive signal (linked to the way it works). What kind of repetitive signal this device loves to trigger ?

2.1. Ethernet signal : my SDS2504++ (500M BW DSO) can trigger an ethernet signal (100Mb is easier to probe the 125MHz than the bi-directional 1Gb) ? but regarding signal between IC & SFP 1Gb (signal @ 1.25GHz), this device can do it ? (given that I have 1GHz active probes, PMK Tetris)
2.2. oscillators analysis ? to check freq stability, a TinyPFA is more precise by 1e3 min order of magnitude... Correct ?
2.3. regarding any "fast" digital signal, to analyse in the time-domain, this scope is more "precise" than any DSO (like my SDS2504X+) thanks to its much lower rise. Correct ?

I'm interested in the jitter (eye-diagram, or pseudo-eye-D) of some basic digital signal :
- USB 2.0 is based on 480MHz signal (SA snifing) => this device can help to get a +/- clear picture of the signal ?
- HDMI 1.4 is based on 650MHz (wrong figure but close, I can't remember the right one) signal (SA snifing) => this device can help to get a +/- clear picture of the signal ?

3. Channel 1 is labeled "trigger". This feature blurs me...
3.1. Why ? a "noob-level" reply is requested, please 
3.2. This "scope" doesn't work like a DSO, but you can plug any probe and you got the pattern on the screen... yes/no ?
3.3 Channel 1 is labeled "trigger" => does it mean that the scope is not able to find by itself that the main pattern is at 125MHz for instance, and then lock to it, do the sampling => and presents the signal on the screen ?

4. what's the trigger jitter of this scope ?

Thanks to anyone to answer these low-level questions... 
Maybe I'm wrong but I see this device as a dead "cheap" alternative to upgrade (to be an add-on, restricted to some signals) a hobbyist-level DSO like a SDS2504X+ (sticker on the scope is 2104X+ of course.. a gem this DSO...)

Thanks for feedback
PS : if I'm wrong here & there => be rude & correct => I just want to learn 

[SJL-Instruments]

Wasn't sure how good your port match is. 

Not the best, to be honest: -17 dB @ 3 GHz (although we don't characterize this on a per-unit basis).
We have a design with better matching (-30 dB) at the cost of 2x noise floor. We opted for the lower-noise design, since you can get essentially the same results with a 6 dB attenuator (but not the other way around).

Thanks points2 for your detailed questions. We'll try to keep our answers succinct but clear.

1. given its limiation due to the way it works => it is a big bargain vs any all-in-one DSO on the market ? correct ?

Yes, if your signal is repetitive (i.e. you can trigger many times - no one-shot signals), and you can pre-trigger or delay your signal.
This is explained in more depth in Section 2.1 of the manual.
If you need to do serial decoding, you need a real-time DSO (or a logic analyzer).
If you're (for example) doing something weird with nanosecond laser pulses, where usually you have high rep rates, the GigaWave will likely do the job.

2.1. Ethernet signal : my SDS2504++ (500M BW DSO) can trigger an ethernet signal (100Mb is easier to probe the 125MHz than the bi-directional 1Gb) ? but regarding signal between IC & SFP 1Gb (signal @ 1.25GHz), this device can do it ? (given that I have 1GHz active probes, PMK Tetris)

Yes, you can trigger on this signal. You can't decode the data (use a logic analyzer), but you can check signal integrity (pseudo-eye-diagram, real eye diagram if you have CDR).

2.2. oscillators analysis ? to check freq stability, a TinyPFA is more precise by 1e3 min order of magnitude... Correct ?

Yes, oscillator stability/jitter/etc is better-suited for frequency-domain tools. The exception is rise/fall time - the GigaWave is great for that.

USB 2.0 is based on 480MHz signal (SA snifing) => this device can help to get a +/- clear picture of the signal ?
- HDMI 1.4 is based on 650MHz (wrong figure but close, I can't remember the right one) signal (SA snifing) => this device can help to get a +/- clear picture of the signal ?

Yes, the GigaWave can generate an eye diagram for these protocols (see caveat on CDR above).
Jitter analysis/mask testing is planned but not yet implemented. We understand if you want to wait for this feature before purchasing.

3. Channel 1 is labeled "trigger". This feature blurs me...
3.1. Why ? a "noob-level" reply is requested, please 

To offer this bandwidth at this price, only Channel 1 has trigger hardware. It is a real channel (i.e. you can plug in a sine wave to CH1 and look at it). You will need to swap around cables to trigger on a different channel.

3.2. This "scope" doesn't work like a DSO, but you can plug any probe and you got the pattern on the screen... yes/no ?

Yes, with the caveats that you can only trigger on CH1, and the signal must be repetitive. (i.e. think about which channel will be the trigger before you set up the cables.)
You can (for example) feed in a clock signal directly to CH1. It will show up, and you can measure its risetime and jitter.
If nothing's plugged into to CH1, nothing will happen.

3.3 Channel 1 is labeled "trigger" => does it mean that the scope is not able to find by itself that the main pattern is at 125MHz for instance, and then lock to it, do the sampling => and presents the signal on the screen ?

If you plug in a 125 MHz square wave into CH1, you'll see a 125 MHz square wave.
If you plug in a 125 MHz data signal, you'll get something resembling an eye diagram (not a "true" eye diagram, though).
If you want to see a repetitive pattern, you'll need some auxiliary clock signal that repeats once per period of the pattern. Then plug the pattern into CH2 and the auxiliary clock into CH1.

4. what's the trigger jitter of this scope ?

Typically 4 ps RMS. This is calibrated per-device, and is listed on the accompanying calibration sheet.
Do note that the effective jitter increases with the timebase delay (i.e. for best jitter, keep the signal before 100 ns on the timebase). The exact formula is in Section 2.3.


In summary:
- This device does not replace a DSO. If you need to look at rare events, or single-shot info, you should buy a realtime DSO.
- If you don't need the bandwidth, buy a realtime DSO or a random sampling scope. The price decreases exponentially with bandwidth.
- But, if your application allows for repetitive triggers, and you're looking at the overall behavior (not single-shot), the GigaWave might work. Things like rise/fall times of clocks, eye diagrams for signal integrity, and any experimental/oddball application requiring picosecond timing are all great applications for the GigaWave.

Thanks for the detailed questions - hope this cleared things up a bit!

[points2]

Hi SLS,
many thanks for your reply, that can help others : Cool !
Sorry again vs the "very jittery" way I exposed "simple" stuff.. so far away from the maestros (joey & many others  )
KRgds

[SJL-Instruments]

It, meaning your products serial interface.

We received a few other requests, so we bumped up the priority of the serial interface guide.
It is now available in Section 4 of the User Manual. (Refresh if it's not updating for you.)
https://www.sjl-instruments.com/user-manual.pdf

Let us know if anything is unclear.

[joeqsmith]

Thank you for taking the time to document the command set.   I had a short conversation with the designer of the LibreVNA.  They also use USB but with a custom class.  Because I never ended up getting one, I spent minimal time looking into it.  I can tell you that your simulated serial interface is a LOT simpler to implement.  The basic command set suggests it would be fairly easy to develop custom software for it. 

[joeqsmith]

After looking at so many low cost VNAs, I am curious what you have done for the connectors.  The  How many mate cycles are they rated for?  Are there concerns about torquing the SMAs? 

Left, my original NanoVNA.  Center, Mini-Circuits attenuator.  Right, my original LiteVNA.    Even though these are inexpensive, I still clean the connectors and minimize how much I touch them.  I also tend to keep the cables attached to them so these have not had a lot of mate cycles.  It does appear that the LiteVNA used a higher quality part.  When you are trying to sell a product for under $150, it is difficult to make a profit using 3.5mm end launch connectors.   

I have never broke a connector by torquing them with normal use.   I've had several people write me suggesting otherwise.  Any concerns on your product?

[SJL-Instruments]

Thanks for asking. The exact connector we use is 901-10512-1 from Amphenol, rated for 26.5 GHz and min 500 cycles (full torque). This is about the best quality you can get for a brass SMA connector.

Torquing the SMAs (with a torque wrench) is not a concern. The aluminum housing is machined to close tolerances, so that the torque is transferred through the housing and does not flex the PCB more than a few thousandths of an inch.

However, if you open the case, torquing against the bare PCB may cause damage.

If anything does occur, worn/broken connectors are also a free warranty repair. Connector savers are always an option if you're paranoid.

[joeqsmith]

My Signal Hound uses USB 3.  It reminds me of Longfellow, There was a little girl.  When she was bad she was horrid.  That pretty much sums up my experiences with USB. 

While I typically like headless equipment, the main problem all of them seem to have, they are headless..     What happens is my PC is on my desktop and what I want to look at is on the bench.   The cable supplied with my Signal Hound was maybe 2' long.  They recommend a direct connection to the PC and warn against   extension cables or use of powered hubs.   How do I use it?  With a powered hub and extension cable.  Took some trial and error to get it stable, or as stable as USB can be. 

Looking at your manual to see what is included, I see no mention of cables.  Assuming you provide one, how long is it?  What interface connector is provided to connect to the PC?  My two PCs for example support USB3.0 type A connectors.  If you don't supply adapters/cables, and if it is critical, what guidelines do you offer? 

[joeqsmith]

How about adding some basic measurements beyond what you have.  P-P for example.   Maybe have a look at what other scopes offer for basic measurements.   I like how even my 80's LeCroy can at the touch of a button throw up a hand full of parameters.   If you don't like those, they offer a pretty broad spectrum of measurements they can make. 

I think John's comment out his 11GHz $1000 DSO

I find it difficult to use, mainly because of the software.

is a case where the UI is VERY important and can brake a product.  Limited features to achieve a simple interface is not IMO a good solution.  I want something feature rich, just easy to drive.   As you said, your software is easy to drive and doesn't require a users to read a novel to run it.  But it also lacks a lot of basic functions.   

****
Let me give you an example of what I consider a problem with your UI.  Say I have some signal that I want to look at.  I have some pre-trigger and want to find the falling edge.  I can't just capture unlimited data so I need to change the delay (timebase position) manually to hunt for it.   In order to do this, I have to type in the delay I want.  There is no inc/dec key.  No way to select how much to inc/dec by.... All manual and very painful.   That, or I am not understanding how it works.   I would expect all of the controls to have an easy way to adjust then outside of typing in the values.  Your trigger level for example allows me to set it by dragging the pointer.

[SJL-Instruments]

Looking at your manual to see what is included, I see no mention of cables.  Assuming you provide one, how long is it?  What interface connector is provided to connect to the PC?  My two PCs for example support USB3.0 type A connectors.  If you don't supply adapters/cables, and if it is critical, what guidelines do you offer? 

The accessory list is provided on the homepage - we'll add it to the manual as well (edit: done), thanks for catching that.
We currently provide a 3' USB-C to USB-C cable and a hex key (for opening/repairing the device).
We don't currently provide a USB-A adapter, but we'll do that in the future - thanks.

We have a sizable factor of safety built into the USB power draw, and we only need USB 2.0 FS comms (12 Mbaud, the "heavy lifting" occurs device-side). We have run the GigaWave over a USB extension cord without issues. It will be interesting to see whether the device runs into issues near your ignition system, but we think it has a good chance of working (fingers crossed).

How about adding some basic measurements beyond what you have.  P-P for example.   Maybe have a look at what other scopes offer for basic measurements.   I like how even my 80's LeCroy can at the touch of a button throw up a hand full of parameters.   If you don't like those, they offer a pretty broad spectrum of measurements they can make. 

I think John's comment out his 11GHz $1000 DSO

I find it difficult to use, mainly because of the software.

is a case where the UI is VERY important and can brake a product.  Limited features to achieve a simple interface is not IMO a good solution.  I want something feature rich, just easy to drive.   As you said, your software is easy to drive and doesn't require a users to read a novel to run it.  But it also lacks a lot of basic functions.   

Thanks for the pointers. We'll implement all the standard measurements (likely by next update).
For P-P specifically, the software already implements this measurement (choose the "Vertical" category when adding a measurement).

Let me give you an example of what I consider a problem with your UI.  Say I have some signal that I want to look at.  I have some pre-trigger and want to find the falling edge.  I can't just capture unlimited data so I need to change the delay (timebase position) manually to hunt for it.   In order to do this, I have to type in the delay I want.  There is no inc/dec key.  No way to select how much to inc/dec by.... All manual and very painful.   That, or I am not understanding how it works.   I would expect all of the controls to have an easy way to adjust then outside of typing in the values.  Your trigger level for example allows me to set it by dragging the pointer.

You can use the scroll wheel (or on touchscreen, pinch horizontally) to zoom out the timebase until you see the falling edge. (Drag the holdoff marker to the right if it doesn't appear within the trigger holdoff.) Then zoom in onto the falling edge, dragging horizontally to shift the timebase. This will center the falling edge nicely with a usable zoom level - no need to type anything.

Of all the controls currently exposed in the main view, only the timebase resolution (points/div) and the trigger direction (rising/falling) actually require you to go click on the setting itself. We'll rewrite the manual to be more clear about all this. We've laid out the controls more clearly in revision H3 of the manual.

Please let us know of any other "basic features" you think are missing - this feedback is extremely helpful.

[joeqsmith]

Thanks, I now see that mouse wheel and selecting the screen and dragging will set the Base and Position.  Same for dragging the offsets.  This is actually quite usable.   My monitors do not support touch but that is good to know if I were to use a tablet to run it.    Also, very good to know about the USB 2.  Sorting a good cable should not be a problem then. 

I had completely missed the Vertical measurements.    

How do I save a waveform to memory and recall it, overlay?  How do I enable persistence?   

***
If you could stream the sweeps to disk and publish the format, that may also be helpful. 
Adding histograms would also be nice to have.   
Allow user to change the measurements rather than having to delete them and create new.
Add markers to waveform showing where the measurements are made.  For example show where the 20/80% points are.

[SJL-Instruments]

How do I save a waveform to memory and recall it, overlay?  How do I enable persistence? 

We don't have these options implemented yet - we'll queue them up for next update (or the one after).
Our immediate thought is to put the waveform save/recall/overlay in the File menu, and persistence as a checkbox in the advanced options for each channel.
Is there an existing UI for these that you particularly like? (This question also applies to your suggestions below.)

If you could stream the sweeps to disk and publish the format, that may also be helpful.
Adding histograms would also be nice to have.   
Allow user to change the measurements rather than having to delete them and create new.
Add markers to waveform showing where the measurements are made.  For example show where the 20/80% points are.

Many thanks for these suggestions. We've added them to the todo list - ETA hopefully 2 weeks for all of these.

[joeqsmith]

Many thanks for these suggestions. We've added them to the todo list - ETA hopefully 2 weeks for all of these.

Big thanks!     

Is there an existing UI for these that you particularly like? (This question also applies to your suggestions below.)

Maybe you could make a poll on this site asking for this kind of input.  Keep it generic and I am sure countless people will provide you with their opinions.   

[points2]

Hi SLJ,
more questions 

1. the USB plug => is type-C
but you provide an adapter usb-C to USB-A
1.1. Does it mean that the USB link is USB.2 ?
1.2. Did you test the performance of the device with different "power supply" :
for instance
=> the USB link
vs
=> a tweaked USB link that enable to get power from an external PS, for instance a "nice" linear PS (less noisy than the power coming from a hub / PC...)

2. Trigger frequency : internal vs external.
I guess this question is valid to any sampling scope... (?)
Is it better to rely on (your advice) =>
2.1. the hardware to find out the trigger frequency & stick to it (timebase + PLL ; given that both have their own jitter)
2.2. OR, using an external clock signal (that match the frequency to trigger) ; for instance, a DIY clock based on a "good" tcxo ? (as I don't deal with >100 different frequencies,    , it is cheap to buy a fixed-frequency oscillator from a vendor..., and quite easy to get a rather good stability)
thanks