Author Topic: Yet another fast edge pulse generator  (Read 28741 times)

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Offline Leo Bodnar

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Re: Yet another fast edge pulse generator
« Reply #200 on: August 18, 2017, 10:36:03 PM »
I also assumed the pulser supplied trace showing a rise-time of 49.2ps for the unit as correct as I do not know the specs of the measuring instrument. I assume it is much better than my old stuff ::)
I have two CSA803A in very good condition, looking almost brand new inside and a variety of sampling heads, one SD-30 (40GHz) and a number of SD-26(20GHz) and SD-22(12.5GHz.)
They are all from different sources and I have cross-checked them against each other - they all agree within noise floor limits. 
This is old equipment from 1990's so it hardly makes any sense to get calibrated, especially for the fun project like this.

I use CSA803A with SD-26 head (17.5ps nominal risetime) installed to print the slips I include with each pulser I send away.
I have tested few units on SD-30 (8.8ps risetime) and there is only 2-3ps difference in the total result - as expected.

Overall I am quite happy with the pulser design performance so will leave it as it is for now.

Leo
« Last Edit: August 18, 2017, 10:37:45 PM by Leo Bodnar »
 

Offline richnormand

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Re: Yet another fast edge pulse generator
« Reply #201 on: August 19, 2017, 05:03:50 AM »
Thanks for the trace information Leo.  :)

The risetime numbers do make sense then, even if I shave a few ps to deconvolve your trace.... well within experimental error.

""Overall I am quite happy with the pulser design performance so will leave it as it is for now.""
Agreed! The unit is a very nice piece of work, don't mess with greatness. :)

I believe my S-6 sampling head with about 10GHz bandwidth is circa 1970s vintage so your equipment is positively modern by my standards :-+

Can't wait to see what you come up with as an encore.

Cheers and thanks.

rich

 

Offline Leo Bodnar

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Re: Yet another fast edge pulse generator
« Reply #202 on: September 02, 2017, 05:07:29 AM »
Gentlemen,

Thanks to all of you who supported me by buying one of the pulsers!

To date,  the feedback was very good, performance was excellent and very stable. 
All current devices show risetime between 40 and 50ps and falltime around 40 ps.

I have received new PCB batch and keep assembling the pulsers to maintain stock levels.  They ship same/next working day.

If you wanted to get one - get it now, there is no guarantee that it will be available forever.

Cheers
Leo

http://www.leobodnar.com/shop/index.php?main_page=product_info&cPath=124&products_id=295
« Last Edit: September 12, 2017, 06:02:25 AM by Leo Bodnar »
 

Offline Leo Bodnar

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Re: Yet another fast edge pulse generator
« Reply #203 on: September 22, 2017, 12:01:59 AM »
Update 21 September 2017.

I have been slightly tweaking the design between the batches to milk a bit more performance out of it.

Latest batch of the pulsers that I have assembled today all show risetime and falltime below 40ps.

I use two CSA803As with two cross-checked SD-30 40GHz sampling heads to individually test each and every unit.

Here are the rising and falling edge screenshots from a typical fully assembled pulser.

If you still want one - get it while you can.

Thank you for your interest, gentlemen.

Leo

« Last Edit: September 22, 2017, 12:16:09 AM by Leo Bodnar »
 
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Offline modmix

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Re: Yet another fast edge pulse generator
« Reply #204 on: September 30, 2017, 08:05:55 PM »
Would like to tell you about my 40psec device received recently.

it comes with printed measurements: Pulser_40psec_Leo_Bodnar_Measurement_web.jpg - awesome  ;)

Unfortunately, my Tektronics 2465B appears to be a bit slow: Pulser_40psec_Leo_Bodnar_2465B_50R_rise_web.jpg
RiseTime => 284 MHz
FallTime =>  320 MHz

My Hameg HM407 is better than spec: Pulser_40psec_Leo_Bodnar_HM407_rise_web.jpg
RiseTime => 41 MHz
FallTime => 45 MHz

Out of curiosity I connected the device to my GPS synced counter:  Pulser_40psec_Leo_Bodnar_52320A_web.jpg
< 32 mHz Allan Deviation is quite good...
Looks like I've got an easily transportable 10 MHz reference in addition  ;)

Cheers
Ulli
« Last Edit: September 30, 2017, 08:07:54 PM by modmix »
 

Offline Howardlong

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Re: Yet another fast edge pulse generator
« Reply #205 on: October 02, 2017, 08:33:06 AM »
There’s a limitation on the 2465B and 2467B auto measurement system which aflicts fast signals.

You’ll have to do it manually with your #1 eyeball and the graticule & cursors, with a vertical vernier and x10 timebase setting I’m afraid to get a decent response.
« Last Edit: October 02, 2017, 08:39:48 AM by Howardlong »
 

Offline Howardlong

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Re: Yet another fast edge pulse generator
« Reply #206 on: October 02, 2017, 08:38:07 AM »
Here's my 2467b

 

Offline EV

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Re: Yet another fast edge pulse generator
« Reply #207 on: October 12, 2017, 12:19:38 AM »
I got my generator today.

Here are measured rise times from my Tektronix scopes 2465B and 7904.
Tek 7904 has 7T11 and 7S11 (with S-4) plug-ins installed. I used internal triggering.
 

Online capt bullshot

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Re: Yet another fast edge pulse generator
« Reply #208 on: October 12, 2017, 05:29:42 AM »
More pictures made with my pulser (first batch):

S4 sampling head / 7S12 in 7603 Mainframe


S2 sampling head / 7S12 in 7603 Mainframe

« Last Edit: October 12, 2017, 06:03:21 AM by capt bullshot »
Safety devices hinder evolution
 

Online capt bullshot

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Re: Yet another fast edge pulse generator
« Reply #209 on: October 12, 2017, 06:00:39 AM »
Two more

Tek 468 in non-store (analog 100MHz BW) mode, 5ns/div


Tek TDS420

« Last Edit: October 12, 2017, 06:02:24 AM by capt bullshot »
Safety devices hinder evolution
 

Offline EV

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Re: Yet another fast edge pulse generator
« Reply #210 on: October 12, 2017, 06:59:59 PM »
Here are rise and fall time pictures from Tektronix TDS3032:
 

Offline macboy

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Re: Yet another fast edge pulse generator
« Reply #211 on: October 13, 2017, 01:59:38 AM »
Tek 2465A  (refer to Buy/Sell forum if you want it!).
 

Online MrW0lf

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Re: Yet another fast edge pulse generator
« Reply #212 on: October 13, 2017, 07:59:46 AM »
50ps pulser + PicoScope 2408B with 50ohm passthru.



...and first experiment. Tried to get actual pulses instead of square. At the end of tower is short:




« Last Edit: October 13, 2017, 08:01:24 AM by MrW0lf »
 

Offline EV

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Re: Yet another fast edge pulse generator
« Reply #213 on: October 13, 2017, 08:37:02 AM »
Tektronix 7103R with 7A29 and 7B15 plug ins. Rise time is about 310 ps.
 
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Offline macboy

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Re: Yet another fast edge pulse generator
« Reply #214 on: October 13, 2017, 09:39:07 AM »
[/img]

...and first experiment. Tried to get actual pulses instead of square. At the end of tower is short:


Impulse response can be mathematically determined from the step response, just differentiate. Then you can get the system frequency response from that impulse response by taking FFT.
 

Online MrW0lf

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Re: Yet another fast edge pulse generator
« Reply #215 on: October 13, 2017, 09:47:12 AM »
Impulse response can be mathematically determined from the step response, just differentiate. Then you can get the system frequency response from that impulse response by taking FFT.

That's another story :) In this case was specifically interested in creating physical pulse, not characterize scope etc. In fact I could not characterize scope in original software with this method anyway because:
It will do derivative just fine. Even agrees to do FFT on it. But due to some bug wont render trace :-BROKE And even if it would no use. FFT trace is hard-limited to 100MHz. Because it is officially 100MHz scope. Actually it is ~140MHz scope of course. I hate when excellent hardware is crippled by "almost there" programming + politics.



Edit: MatLab seems to do the supposed thing, 3.2dB diff 10MHz vs 150MHz:

« Last Edit: October 13, 2017, 09:54:55 PM by MrW0lf »
 

Offline EV

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Re: Yet another fast edge pulse generator
« Reply #216 on: October 13, 2017, 05:50:01 PM »
Here is rise time for Tektronix 2247A:
 

Offline macboy

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Re: Yet another fast edge pulse generator
« Reply #217 on: October 14, 2017, 12:58:50 AM »
Here are a couple of screenshots from my Lecroy WavePro 960 (2 GHz, 16 GS/s).
Trace "A" is an average of the channel under test (for noise reduction).
Trace "B" is the derivative d/dt of A. Note the vertical scale of 1 GV/s per div!
Trace "C" is the FFT of B.
Trace C gives the frequency response of the oscilloscope and pulser (and any cable connecting them, none in this case).

Trace A shows rise time of 268 ps. Using the relation 0.45/Tr=BW, it estimates 1.68 GHz. Obviously such rules of thumb are not universally applicable. The actual -3 dB point in Trace C is 2.03 Ghz.

It can be shown mathematically that an impulse has equal energy at all frequencies. So, if you pass an impulse through a system, you can measure the frequency response by looking at what went through. Generating an actual impulse is impractical, largely because generating one with enough energy to measure practically presents difficulties. For example, an impulse that delivering the same energy to the system as does a 50 ps 1 V rising edge, would require a 50 ps wide, 20 000 000 000 volt pulse. I can't generate 20 GV in my lab, and my scope input wouldn't like it if I could  :scared:  Actually, we don't quite need that much energy but it is still difficult to generate a well-behaved impulse. Fortunately, we can use math trickery instead. We know that the d/dt of a step is an impulse. The "d/dt of the response to a step" is the same as the "response to the d/dt of a step" (response to an impulse). So we apply a fast rise step to the system, measure system step response, then take d/dt of the step response to get the system impulse response. Then convert to frequency domain (take FFT) to get frequency response. That is exactly what is shown in Trace C.

In this case, the frequency response can be seen varying about +/- 1 dB from zero to 2 GHz, and dropping extremely rapidly after 2 GHz. The -3 dB point relative to DC is 2.03 GHz.

I have a variable filter (Krohn Hite 3202r), which can do high pass, low pass, bandpass, and notch modes with a continuously variable corner/center frequency. It can be entertaining to set up the scope to display the frequency response in real time while playing with the filters.

p.s. MrW0lf, confine your FFT to a single period and you'll get the nice flat-top result. In this case, you want the DC imbalance that is present in the impulse response.



« Last Edit: November 01, 2017, 02:00:26 AM by macboy »
 
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Online MrW0lf

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Re: Yet another fast edge pulse generator
« Reply #218 on: October 14, 2017, 02:15:39 AM »
macboy, thanks for clarifications. I will play with pulser later and try to reproduce by-the-book result. Have not tried this before because of software issues. Only recently got MatLab because stuff not doable in original software started to pile up.

BTW I had to use multiple periods because just extracted raw data - 1GSa/s non averaged is not sufficent - small number of periods will just show garbage.

As for my original physical impulse shot - I have interest in solitons, but no fancy indoor waveguide:


So have to do it small and with electricity much like this:
https://youtu.be/I9m2w4DgeVk?t=11m46s
 

Offline zucca

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Re: Yet another fast edge pulse generator
« Reply #219 on: October 14, 2017, 02:33:21 AM »
TEA got me again, I just ordered one.

Very interesting  results. Since I am pretty virgin on this topic:

https://www.edn.com/electronics-blogs/bogatin-s-rules-of-thumb/4424573/Rule-of-Thumb--1--The-bandwidth-of-a-signal-from-its-rise-time

http://literature.cdn.keysight.com/litweb/pdf/5988-8008EN.pdf

Sorry if was already posted somewhere here...

EDIT:
of course was already there:
http://www.eevblog.com/forum/projects/yet-another-fast-edge-pulse-generator/msg1271710/?topicseen#msg1271710

EDIT2:
@Leo Bodnar, Did you post it in the Buy/sell section? I coudn't find it, such a nice product deserves more customers...
« Last Edit: October 14, 2017, 03:59:15 AM by zucca »
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Can't love what you don't know. Zucca
 

Online MrW0lf

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Re: Yet another fast edge pulse generator
« Reply #220 on: October 14, 2017, 06:23:08 AM »
Ok, tried hard to get it right:

ETS monster style: 20GSa/s, single wfm (zoomed), averaged, 1kpts:

Get nice smooth graph but overly optimistic.

RTS style: 1GSa/s, many wfms (zoomed on single), averaged, 1Mpts:

Detailed FFT, quite realistic result.

Possibly there are issues with approach MatLab Signal Analyzer uses:
https://se.mathworks.com/help/signal/ug/spectrum-computation-in-signal-analyzer.html

Interesting which low end scopes could actually pull this off in native GUI? GW Instek possibly? It's a shame Picos cant do it - its not by design but by some stupid bug :(
« Last Edit: October 14, 2017, 06:45:05 AM by MrW0lf »
 

Offline EV

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Re: Yet another fast edge pulse generator
« Reply #221 on: October 15, 2017, 03:42:57 AM »
Here is rise time from Tektronix 7904 with plug ins 7A29 and 7B92A. It is about 600 ps.
 

Offline Leo Bodnar

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Re: Yet another fast edge pulse generator
« Reply #222 on: October 19, 2017, 07:42:57 AM »
I have been to the Electronics Design Show in Coventry (UK) earlier today and dropped by our friends from Tektronix and Pico Technology.

Thanks to James from Tek and Kieran and Trevor from Pico Tech for testing the pulser.  It is not easy to demo your complicated top line equipment live when everybody is watching - especially to test a surprise customer device.  When I have showed up both scopes were set up to run demos for eye pattern tests and TDR but engineers were more than happy to rip the setup apart and connect my unknown DUT - both scopes worked flawlessly and we had great fun.

Tektronix had 33GHz BW, 100Gsps realtime DPO73304SX scope on their stand and the pulser edge speed result was 31ps.

Pico Technology demoed 20GHz BW sampling scope with TDR capability which measured the pulser risetime at 34ps.

Leo

Online HighVoltage

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Re: Yet another fast edge pulse generator
« Reply #223 on: October 19, 2017, 08:47:41 AM »
What a nice opportunity top test your pulse generator.
And great pictures, thanks for sharing.

There are 3 kinds of people in this world, those who can count and those who can not.
 

Online MrW0lf

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Re: Yet another fast edge pulse generator
« Reply #224 on: October 19, 2017, 09:11:08 AM »
BTW, later I managed to partially work around fft(derivative(signal)) issue on Pico RTS range software also, described here. Hope in future some wizardry gone into ETS software can be channeled down the range so could do fun stuff with less effort.
 


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