Yet another fast edge pulse generator

[Converter]

The rise time on this one was recorded at 33.99pS.

33.99 ps? Okay, we will assume that 34ps.
Then own rise time of your generator is approximately ~29.2ps. And the rise time of your oscilloscope (DSO81204B) is ~33.9ps.

I mean the following:
Tr_(sampler) = [Tr2 _(obs) - Tr2 _(pulser) - Tr2 _(jitter) ]^1/2

√ (44.76² - 29.2²) = √1150.8 = 33.92 ps.
*I ignored the jitter

[Leo Bodnar]

I have done a small prototyping run of a version with 2.92mm connector.

Rise time is 30ps±1ps for a 1Vpp pulse as seen by 50? load. Pulses are 10MHz 50% duty negative going (levels are 0V and -1V.)
Test system is CSA803A with SD-30 sampling head (T_rt=8.8ps.)

If there is interest I can assemble few more pulsers with 2.92mm or SMA connectors and make them available for sale. 
The cost is £99 for 2.92mm connector and £90 for SMA connector version.  This will include 18GHz SMA plug-to-plug adaptor like this one that pulser will be tested with.  I have a few 2.92mm adapters and the difference between them and good quality SMA one is really tiny.

Thanks
Leo

[KE5FX]

If there is interest I can assemble few more pulsers with 2.92mm or SMA connectors and make them available for sale

I'd take one of the 2.92mm units.  That connector looks good, might be interesting to play with it.

[Leo Bodnar]

Cool, thank you for your interest.

Fall time is around 25ps at the expense of slightly rougher undershoot.

Leo

[moore]

I'd also be interested in a 2.92mm version.  Any idea when they would be available ... if you've even decided to go ahead that is?

[Berni]

I would be interested in buying a SMA version.

[HighVoltage]

I interested in buying a SMA version.

[texaspyro]

Out of curiosity, I connected a pulser to a TAPR TICC through a TADD-2 mini divider to get a 1Hz output and used Lady Heather to analyze the output frequency.   My pulser wanders around a 1.05 Hz interval from an average 10,000,001.9 Hz.   Attached is a plot and ADEVs of the pulser output.  The frequency plot shows the error from the nominal 10 MHz freq.  The TICC reference clock was an HP5071 cesium beam oscillator.

[jhenderson0107]

I am interested in an SMA version also. 

[Leo Bodnar]

Thanks for everyone's interest, guys.

The best way to get one is to place an order online and it will ship in a FIFO manner.  I have enough confidence in SMA/2.92mm version to offer it for sale now.

I usually ship immediately but SMA and 2.92mm will take a few days while I am assembling and testing them this week.

2.92mm: http://www.leobodnar.com/shop/index.php?main_page=product_info&cPath=124&products_id=302
SMA: http://www.leobodnar.com/shop/index.php?main_page=product_info&cPath=124&products_id=303
BNC: http://www.leobodnar.com/shop/index.php?main_page=product_info&cPath=124&products_id=295

Cheers
Leo

I am interested in an SMA version also.

[Bitstream]

Got my pulse generator today -very nice quality construction!   

Two more scopes to add to the list:

Keysight MSOX-4054A: tRISE=664pS,  Bandwidth =0.35/664E-12 =527 MHz.  Channel 1 is shown.  Channels 2-3 were about the same & channel 4 was 550 MHz.

Tektronix 7104 + 7A29 1GHz plugin:  tRISE=360pS, Bandwidth =0.35/360E-12 =972MHz.  Not bad given the scope hasn't been calibrated in about 5 years.

[KE5FX]

  I have enough confidence in SMA/2.92mm version to offer it for sale now.

Fast service in more ways than one! 

[texaspyro]

More curiosity inquiring...  the room temperature has been changing a few degrees over 24 hours lately and I measured the tempco of the pulser output freq.  Seems to be around 0.2 Hz per degree C. 

[HighVoltage]

The SMA version I ordered, arrived yesterday.
Thank you!

Today I compared all three of your pulse generators on my Keysight 6000X scope.
The serial numbers are:

Pulser#    Serial    Type    RT            FT
---------------------------------------------
Pulser-1: P00016, BNC    78.8 ps,     77.9 ps
Pulser-2: P00043, BNC    81.6 ps,     80.9 ps
Pulser-3: P10007, SMA    80.2 ps,     80.8 ps

Interestingly, on the SMA Pulser-3, the waveform has shifted down by 500 mV
More interesting, the very first one you made for me is the fastest right now.

[Leo Bodnar]

Interestingly, on the SMA Pulser-3, the waveform has shifted down by 500 mV
More interesting, the very first one you made for me is the fastest right now.

SMA and 2.92mm versions are DC coupled and have negative going pulse.
Try playing with output levels and see if this affects the risetime.
Are you using inter-series adapters?
Cheers
Leo

[Berni]

I just got mine yesterday and i again got numbers pretty close to the included calibration screenshot on my 20GHz HP sampling scope.

I did take notice that there is an offset now and that the output of the chip looks like it goes directly to the output. Neat wide supply decoupling caps around that chip by the way, im guessing those have lower impedance than regular ones. I don't mind the offset, but if i wanted to get rid of it i can still use a 18GHz DC block that i have somewhere.

By the way since the MCU is running the show is it possible to also have it output lower frequencies now that there is no coupling cap. Haven't found myself needing it but i would imagine some could find it useful for checking long runs of coax cables for damage.

[Leo Bodnar]

By the way since the MCU is running the show is it possible to also have it output lower frequencies now that there is no coupling cap. Haven't found myself needing it but i would imagine some could find it useful for checking long runs of coax cables for damage.

Pulse train is still taken directly from TCXO.  I might design a variable pulse length version at some point but it is not too trivial as I'd like to maintain low jitter for those of us who use sampling scopes. Low as in no more than a few picoseconds.
Leo

[richnormand]

 as I'd like to maintain low jitter for those of us who use sampling scopes. Low as in no more than a few picoseconds.
Leo

Fully agree here considering the way I use it.
Got your first version and I was quite impressed about that point about the trigger reliability and consistent timing.
Cheers

[Berni]

Ah that's for the best then.

For fault finding coax cables you probably don't need a pulse that sharp anyway.

[borjam]

Siglent SDS-1202X-E

With a HP 10100C 50 ohm terminator and without terminator.

Rigol DS1074Z (100 MHz)

With terminator and without terminator


Playing with this I noticed something really odd in the Rigol scope. When it allows the operator to enable or disable the sin(x)/x interpolation it does affect the dots display, not just the vector display, which is wrong as far as I know. The dots display is supposed to show just samples. Or should be, right?

[tautech]

Playing with this I noticed something really odd in the Rigol scope. When it allows the operator to enable or disable the sin(x)/x interpolation it does affect the dots display, not just the vector display, which is wrong as far as I know. The dots display is supposed to show just samples. Or should be, right?

Yes, should be just sample points.

rf-loop has mentioned this a few times and using his login in 'By user' for a search and 'fake dots' will find his posts about this.

[zike]

I finally got round to testing a BNC-equipped unit received from Leo on 1/23/18.

By request, this unit was set up for 1.0Vpp output. Leo noted on its included docs that rise time at this high output amplitude is degraded to ~60 ps. However I also noticed from the included test plot that, as an apparent side effect, aberrations in the first ns appear to be well under 2% p-p with this setup. Leo's CSA803 showed very nearly a perfect step.

Many appear obsessed only with rise time; in my experience, a clean top without overshoot is critical for the risetime to be quantitatively meaningful. A dead flat top is an extremely rare and valuable property in a sub-100ps signal source.

I  checked it for myself with a Tek S6 sampling head in a 7S11/7T11/7904 rig, approximately confirming both the reported rise time and measured flatness.  I count about 65 ps intrinsic after RSS regressing the nominal S6 response, and about 3% p-p aberration in the first 250 ps. (I suspect my SMA terminator of some mischief at about 300ps; the S6 loops the signal back out to an external termination, to allow for TDR applications.) 

First 3 attachments show the rise at 50, 200 and 1000 ps/div. Fourth photo shows the fall,  significantly faster at about 40 ps (after RSS regression), but including about 7% p-p aberration. 

For kicks, the fifth shot is an S-52 tunnel diode (25 ps), and sixth is a home-brew pulser using a Russian GI308D tunnel diode (about 75 ps).

Bottom line: With 1Vp-p amplitude, this unit gives ~60 ps rise with damned near perfect shape, and ~40 ps fall with a little aberration. Win-win. Many thanks, Leo!

-Mike

[borjam]

rf-loop has mentioned this a few times and using his login in 'By user' for a search and 'fake dots' will find his posts about this.

Yep, I noticed. You get to choose between fake dots or fake warranty when choosing a cheap scope.

[borjam]

I forgot, @Leo Bodnar

Any plans to release the USB command set so that anyone can write a control program? I am not a Windows user and being able to access it from a Python program would be really useful!

[rhb]

Some screen shots from my DSOs

GW Instek GDS-2702E     V 1.24 FW
GW Instek  MSO-2204EA V 1.32 FW
Rigol DS1102E                   V 0.4.2 SP1 FW

Pulser set as shipped by Leo.  All the scopes meet the specs by a reasonable margin.  The 2072E is considerably more than 70 Mhz, but I don't like the top on either of the Insteks.

 I can't say how much I appreciate that Leo sells these. Having attempted to build one 25 years ago and failed miserably, I have a certain appreciation for the problems such things pose.  My sole, very minor, grumble is I would like to have had a cover over the SMD parts to protect them from damage.  I was going to install a small metal plate using longer screws, but they appear to be staked in place.  But I'll make a U shape clip and epoxy it in place instead.

It would certainly be nice to have the ability to change the frequency of the square wave, but I've got an old scope time base calibrator which accepts an external reference and one of Leo's GPSDOs, so not really needed.  Besides which, the GPSDO will do the job as is.

All the screenshots were made with a 50 ohm terminator and a tee as I don't have a 50 ohm thru terminator.  I had one I'd made, but I stripped it for the Pomona box I'd built in.  And for this sort of task I wouldn't have trusted it anyway.