How to make a super fast sampling head?

On Jan 11, 9:59 pm, Joerg <notthisjoerg...@removethispacbell.net>
wrote:

John Larkin wrote:
On Fri, 11 Jan 2008 11:36:27 -0800 (PST), blackhead
larryhar...@softhome.net> wrote:

On Jan 10, 4:57 pm, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?
It seems complete and utter madness doing this stuff discretely in
this day and age.

The only thing I can say to counter your statement is that we do
picosecond electronics discretely in this day and age, and charge lots
of money for it. At the low to moderate quantity that specialized
electronics is sold, and the cost/yield of custom GaAs and other
exotic materials, discrete design is perfectly reasonable.

Surface-mount parts are so small and fast they have pretty much
destroyed the hybrid business; the Tek 20-50 GHz sampling heads were
hybrids. The "wall in the sky" for surface-mount design is at about
100 picoseconds, where things start to get tough.

AFAIK even stuff like this is done on circuit board (but not FR-4):http://www.ahsystems.com/catalog/data/pdf/PAM-1840.pdf

I used to love hybrids, designed some of them. Active laser trim is a
fantastic design tool, you can do things you wouldn't even dream about
in regular design or chip design. But yeah, in the early 90's the bottom
fell out of that business :-(



You'll have more problems getting the signal into a
fast ADC, without distortion.

The point of equivalent-time sampling is that the adc can be
arbitrarily slow; the front-end acts as a picosecond-gate
sample-and-hold.

Really, all you need is the Digikey catalog and ebay and some
persistance to build good high-speed signal processing stuff.

Plus one minor detail: Potential customers with enough budget.

Tell me about it - though my 500psec sampling head was stroboscopic
electron microscope, which sold for about $100,000 dollars before we
added our timing and data-collecting electronics.

--
Bill Sloman, Nijmegen

 

[Joerg]

John Larkin wrote:

On Fri, 11 Jan 2008 11:36:27 -0800 (PST), blackhead
larryharson@softhome.net> wrote:

On Jan 10, 4:57 pm, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?
It seems complete and utter madness doing this stuff discretely in
this day and age.


The only thing I can say to counter your statement is that we do
picosecond electronics discretely in this day and age, and charge lots
of money for it. At the low to moderate quantity that specialized
electronics is sold, and the cost/yield of custom GaAs and other
exotic materials, discrete design is perfectly reasonable.

Surface-mount parts are so small and fast they have pretty much
destroyed the hybrid business; the Tek 20-50 GHz sampling heads were
hybrids. The "wall in the sky" for surface-mount design is at about
100 picoseconds, where things start to get tough.

AFAIK even stuff like this is done on circuit board (but not FR-4):
http://www.ahsystems.com/catalog/data/pdf/PAM-1840.pdf

I used to love hybrids, designed some of them. Active laser trim is a
fantastic design tool, you can do things you wouldn't even dream about
in regular design or chip design. But yeah, in the early 90's the bottom
fell out of that business :-(

You'll have more problems getting the signal into a
fast ADC, without distortion.

The point of equivalent-time sampling is that the adc can be
arbitrarily slow; the front-end acts as a picosecond-gate
sample-and-hold.


Really, all you need is the Digikey catalog and ebay and some
persistance to build good high-speed signal processing stuff.

Plus one minor detail: Potential customers with enough budget.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

John Larkin wrote:

On Fri, 11 Jan 2008 20:00:33 GMT, Joerg
notthisjoergsch@removethispacbell.net> wrote:

blackhead wrote:
On Jan 10, 4:57 pm, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?
It seems complete and utter madness doing this stuff discretely in
this day and age. You'll have more problems getting the signal into a
fast ADC, without distortion.

So, how do you build a 50psec sampler non-discrete?

The fastest samplers, well above 250 GHz by now, are custom GaAs
parts. They use a nonlinear transmission line (shock line) to sharpen
the edge from an external SRD, and integrate the sampling diodes at
the end. Megabucks of engineering.

Agoston Agoston, of Hyperlabs and formerly Tek, did a 20 GHz sampler
on FR-4 with surface mount parts, at least 10 years ago. It looks like
any ordinary pc board.

Tek and HP sort of called a truce at about 70 GHz, probably because
signals this fast berely go through coax or connectors. PSPL sells a
100 GHz shockline sampler, and I think maybe LeCroy has built a scope
around it.

Ok, full custom it can be done, of course. But that's mega-bucks just in
NRE before you even have anything on the bench.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

John Larkin wrote:

On Fri, 11 Jan 2008 17:55:10 GMT, Joerg
notthisjoergsch@removethispacbell.net> wrote:


PHEMTS on the other hand are phenomenal. Today I was testing a cheap
NEC part, NE3509M04. Gate capacitance measures under 0.8 pF, drain is
about 0.35, Rds-on is about 6 ohms at zero gate voltage, and it
switches on/off fast and clean with ecl-type gate swings. It has no
equivalent of bipolar saturation delay; pull the gate to -0.4, and it
just turns off.

Thanks! Entered into my Dear Santa list.

In stock at Digikey.

Nope, you guys must have cleaned them out.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Spehro Pefhany]

On Fri, 11 Jan 2008 12:04:44 -0800, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Fri, 11 Jan 2008 17:55:10 GMT, Joerg
notthisjoergsch@removethispacbell.net> wrote:


PHEMTS on the other hand are phenomenal. Today I was testing a cheap
NEC part, NE3509M04. Gate capacitance measures under 0.8 pF, drain is
about 0.35, Rds-on is about 6 ohms at zero gate voltage, and it
switches on/off fast and clean with ecl-type gate swings. It has no
equivalent of bipolar saturation delay; pull the gate to -0.4, and it
just turns off.


Thanks! Entered into my Dear Santa list.

In stock at Digikey.

John

Your recommendation seems to have cleaned them out.

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

[John Larkin]

On Fri, 11 Jan 2008 20:00:33 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

blackhead wrote:
On Jan 10, 4:57 pm, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

It seems complete and utter madness doing this stuff discretely in
this day and age. You'll have more problems getting the signal into a
fast ADC, without distortion.


So, how do you build a 50psec sampler non-discrete?

The fastest samplers, well above 250 GHz by now, are custom GaAs
parts. They use a nonlinear transmission line (shock line) to sharpen
the edge from an external SRD, and integrate the sampling diodes at
the end. Megabucks of engineering.

Agoston Agoston, of Hyperlabs and formerly Tek, did a 20 GHz sampler
on FR-4 with surface mount parts, at least 10 years ago. It looks like
any ordinary pc board.

Tek and HP sort of called a truce at about 70 GHz, probably because
signals this fast berely go through coax or connectors. PSPL sells a
100 GHz shockline sampler, and I think maybe LeCroy has built a scope
around it.

John

 

[John Larkin]

On Fri, 11 Jan 2008 17:55:10 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

PHEMTS on the other hand are phenomenal. Today I was testing a cheap
NEC part, NE3509M04. Gate capacitance measures under 0.8 pF, drain is
about 0.35, Rds-on is about 6 ohms at zero gate voltage, and it
switches on/off fast and clean with ecl-type gate swings. It has no
equivalent of bipolar saturation delay; pull the gate to -0.4, and it
just turns off.


Thanks! Entered into my Dear Santa list.

In stock at Digikey.

John

 

[John Larkin]

On Fri, 11 Jan 2008 11:36:27 -0800 (PST), blackhead
<larryharson@softhome.net> wrote:

On Jan 10, 4:57 pm, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

It seems complete and utter madness doing this stuff discretely in
this day and age.

The only thing I can say to counter your statement is that we do
picosecond electronics discretely in this day and age, and charge lots
of money for it. At the low to moderate quantity that specialized
electronics is sold, and the cost/yield of custom GaAs and other
exotic materials, discrete design is perfectly reasonable.

Surface-mount parts are so small and fast they have pretty much
destroyed the hybrid business; the Tek 20-50 GHz sampling heads were
hybrids. The "wall in the sky" for surface-mount design is at about
100 picoseconds, where things start to get tough.

You'll have more problems getting the signal into a
fast ADC, without distortion.

The point of equivalent-time sampling is that the adc can be
arbitrarily slow; the front-end acts as a picosecond-gate
sample-and-hold.


Really, all you need is the Digikey catalog and ebay and some
persistance to build good high-speed signal processing stuff.

John

 

[Joerg]

blackhead wrote:

On Jan 10, 4:57 pm, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

It seems complete and utter madness doing this stuff discretely in
this day and age. You'll have more problems getting the signal into a
fast ADC, without distortion.

So, how do you build a 50psec sampler non-discrete?

--
Regards, Joerg

http://www.analogconsultants.com/

 

[blackhead]

On Jan 10, 4:57 pm, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote:

J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

It seems complete and utter madness doing this stuff discretely in
this day and age. You'll have more problems getting the signal into a
fast ADC, without distortion.

 

[Joerg]

John Larkin wrote:

On Thu, 10 Jan 2008 22:44:16 GMT, Joerg
notthisjoergsch@removethispacbell.net> wrote:

Jan Panteltje wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

Another part you might want to look at are those blazingly fast
transistors from your companies over there, Infineon and NXP. For
example the BFP620. Ok, it's a bipolar transistor but it sports a
whopping 65GHz ft and is very cheap. Just don't push it much past 2V.

I've played with the 45 GHz SiGe bipolars, and always found them to be
slow as time-domain amps or switches. And they love to oscillate in
wideband circuits.

I haven't tried the BFP620 yet, running other tests right now. So far my
projects don't require more than the BFS17 or maybe the BFR93. But even
6GHz ft is probably considered a slowpoke in your world.

PHEMTS on the other hand are phenomenal. Today I was testing a cheap
NEC part, NE3509M04. Gate capacitance measures under 0.8 pF, drain is
about 0.35, Rds-on is about 6 ohms at zero gate voltage, and it
switches on/off fast and clean with ecl-type gate swings. It has no
equivalent of bipolar saturation delay; pull the gate to -0.4, and it
just turns off.

Thanks! Entered into my Dear Santa list.

The weird thing is that Rds-on has a negative TC. I've never seen a
fet do that before.

(Used my trusty old green Boonton analog c-meter. The bottom meter
range is 0 to 1 pF, and it has provision for offsetting strays, 2/4
terminal measurements, and dc bias injection.)

I am using my dipmeter for small Cs. Sometimes the analyzer but that
thing makes such a racket with its airflow.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

Jan Panteltje wrote:

On a sunny day (Thu, 10 Jan 2008 14:21:32 -0800) it happened John Larkin
jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in
ae6do3t2ql5qj0a75j1g051hdoij4nlatt@4ax.com>:

mm 80Ghz! wow.

Good stuff. But check you bank account before ordering
Skyworks SMS7621-079, 0.25 pF schottky. I have a reel of them, 23
cents each.

John

Great, can afford 4 of those I think.

Hey, even a shotglass of Beerenburger with Friese Nagelkaas ist over
four Euros these days ...

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Jan Panteltje]

On a sunny day (Thu, 10 Jan 2008 22:39:15 GMT) it happened Joerg
<notthisjoergsch@removethispacbell.net> wrote in
<n8xhj.7255$pA7.3695@newssvr25.news.prodigy.net>:

Skyworks SMS7621-079, 0.25 pF schottky. I have a reel of them, 23
cents each.


Neat! That's a great deal.

Jan, in Europe you can get this brand via BFI Optilas.

Found them in .nl, their wesite sucks though.

In case you want
to look these up:
http://www.skyworksinc.com/products_display_item.asp?did=798

Got the pdf, needs some reading and getting used to very low inductances
like .3 nH

 

[Jan Panteltje]

On a sunny day (Thu, 10 Jan 2008 14:21:32 -0800) it happened John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in
<ae6do3t2ql5qj0a75j1g051hdoij4nlatt@4ax.com>:

mm 80Ghz! wow.


Good stuff. But check you bank account before ordering

Skyworks SMS7621-079, 0.25 pF schottky. I have a reel of them, 23
cents each.

John

Great, can afford 4 of those I think.

 

[John Larkin]

On Thu, 10 Jan 2008 22:44:16 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

Jan Panteltje wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?


Another part you might want to look at are those blazingly fast
transistors from your companies over there, Infineon and NXP. For
example the BFP620. Ok, it's a bipolar transistor but it sports a
whopping 65GHz ft and is very cheap. Just don't push it much past 2V.

I've played with the 45 GHz SiGe bipolars, and always found them to be
slow as time-domain amps or switches. And they love to oscillate in
wideband circuits.

PHEMTS on the other hand are phenomenal. Today I was testing a cheap
NEC part, NE3509M04. Gate capacitance measures under 0.8 pF, drain is
about 0.35, Rds-on is about 6 ohms at zero gate voltage, and it
switches on/off fast and clean with ecl-type gate swings. It has no
equivalent of bipolar saturation delay; pull the gate to -0.4, and it
just turns off.

The weird thing is that Rds-on has a negative TC. I've never seen a
fet do that before.

(Used my trusty old green Boonton analog c-meter. The bottom meter
range is 0 to 1 pF, and it has provision for offsetting strays, 2/4
terminal measurements, and dc bias injection.)

John

 

On Jan 10, 9:45 pm, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote:

On a sunny day (Thu, 10 Jan 2008 12:22:19 -0800) it happened John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote in
k6vco3dd3f2vpofu683olc3gj6a7ll1...@4ax.com>:





On Thu, 10 Jan 2008 17:51:19 GMT, Joerg
notthisjoerg...@removethispacbell.net> wrote:

Jan Panteltje wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

Usually a transistor that avalanches nicely, a chunk of good coax and
blazingly fast diodes, preferable a matched quad.

I did one with a step-recovery diode impulse generator, feeding a
2-diode sampler. Got 70 ps risetime, roughly 5 GHz, and apparently
good waveform fidelity. The parts cost is tiny, but it's labor
intensive. The timebase and trigger stuff is more work than the
sampler.

The older Tek sampling stuff, the S-series heads and their 7000-series
plugins, are dirt cheap on ebay. But not nearly as nice and
quantitative as the 11801-series stuff.

I doubt you could make a head that would work in an 11801 frame; the
interface is undefined.

It would be fun to do a sampling scope/TDR as a USB dongle.

John

I had some idea (not had much sleep, and then barriers do not
function on my ideas) to make a small PIC scope, say one PIC,
one graphics display (found one dirt cheap), and because PIC will
not digitise faster then a few kHz perhaps, add a sampling head just for fun.
I think the main problem is in the timebase, to do it digitally, and have
it set so it actually produces a steady picture on a repetitive signal,
could be very difficult.

I've done it twice - once for real, with an 800MHz clock and GaAs
counters for the coarse intervals and a built in time to voltage
converter to work out when the trigger arrived within the the 1.25nsec
clock period. My 800MHz clock was poor and we had about 60psec of
jitter on the sampling edges.

A few years later I redesigned the delay-generating part of the
circuit around a 500MHz clock (which would have been crystal
controlled with less than a picosecond of jitter) and ECLinPS counters
for the digital part of the delay, and I was planning on using the
MC100E195 for the fine delays - it offered 2nsec of delay range and
20psec resolution. The MC100EP195 looks even nicer.

The delays through the MC100E195 are temperature dependent, and the
design did depend on recalibrating these delays against the crystal
controlled clock every few minutes, by using the system to set up a
pulse-width modulated waveform and digitising the DC level to find
what each delay really was. We should have been able to run through
all 128 discrete delays within a millisecond or so.

The schematics had been passed on for printed circuit layout when the
customer backed out.

The MC100E196 offers infinite resolution, but would need even more
calibration.

--
Bill Sloman, Nijmegen

 

[Joerg]

bill.sloman@ieee.org wrote:

On Jan 10, 9:45 pm, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote:
On a sunny day (Thu, 10 Jan 2008 12:22:19 -0800) it happened John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote in
k6vco3dd3f2vpofu683olc3gj6a7ll1...@4ax.com>:





On Thu, 10 Jan 2008 17:51:19 GMT, Joerg
notthisjoerg...@removethispacbell.net> wrote:
Jan Panteltje wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?
Usually a transistor that avalanches nicely, a chunk of good coax and
blazingly fast diodes, preferable a matched quad.
I did one with a step-recovery diode impulse generator, feeding a
2-diode sampler. Got 70 ps risetime, roughly 5 GHz, and apparently
good waveform fidelity. The parts cost is tiny, but it's labor
intensive. The timebase and trigger stuff is more work than the
sampler.
The older Tek sampling stuff, the S-series heads and their 7000-series
plugins, are dirt cheap on ebay. But not nearly as nice and
quantitative as the 11801-series stuff.
I doubt you could make a head that would work in an 11801 frame; the
interface is undefined.
It would be fun to do a sampling scope/TDR as a USB dongle.
John
I had some idea (not had much sleep, and then barriers do not
function on my ideas) to make a small PIC scope, say one PIC,
one graphics display (found one dirt cheap), and because PIC will
not digitise faster then a few kHz perhaps, add a sampling head just for fun.
I think the main problem is in the timebase, to do it digitally, and have
it set so it actually produces a steady picture on a repetitive signal,
could be very difficult.

I've done it twice - once for real, with an 800MHz clock and GaAs
counters for the coarse intervals and a built in time to voltage
converter to work out when the trigger arrived within the the 1.25nsec
clock period. My 800MHz clock was poor and we had about 60psec of
jitter on the sampling edges.

A few years later I redesigned the delay-generating part of the
circuit around a 500MHz clock (which would have been crystal
controlled with less than a picosecond of jitter) and ECLinPS counters
for the digital part of the delay, and I was planning on using the
MC100E195 for the fine delays - it offered 2nsec of delay range and
20psec resolution. The MC100EP195 looks even nicer.

The delays through the MC100E195 are temperature dependent, and the
design did depend on recalibrating these delays against the crystal
controlled clock every few minutes, by using the system to set up a
pulse-width modulated waveform and digitising the DC level to find
what each delay really was. We should have been able to run through
all 128 discrete delays within a millisecond or so.

That's where an electronically controlled servoed delay line comes in,
to do the calibration automatically.

The schematics had been passed on for printed circuit layout when the
customer backed out.

The MC100E196 offers infinite resolution, but would need even more
calibration.

--
Bill Sloman, Nijmegen

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Phil Hobbs]

John Larkin wrote:

Do you have Mark Kahr's paper on the history of samplers? The
technology dates back to the 1800's.

http://www.caip.rutgers.edu/~kahrs/books/sampling.html

John

No, I didn't, but I'll download it, thanks. The 19th century example is

the dynamo waveform plotter, I expect. Nice piece of work.

Looking down the list of references, I know a couple of those guys: Mark
Rodwell and I were grad students together--he's now at UCSB trying to
make 1-THz InP bipolars; Dave Bloom was on my PhD committee, and has
retired to Montana after making a pile in the telecom boom.

One missing person is Sadeg Faris, the guy who started Hypres--they had
a SQUID-based sampling scope with (iirc) 70 GHz bandwidth back in the
late 80s. It was a cool gizmo--the input card was about 2 inches long,
and went from room temperature at one end to liquid helium at the other.
Another pair are Dan Grishkowsky and Jean-Marc Halbout, who pioneered
picosecond plasma-optical sampling back in the mid-80s.

Cheers,

Phil Hobbs

 

[Joerg]

Jan Panteltje wrote:

J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

Another part you might want to look at are those blazingly fast
transistors from your companies over there, Infineon and NXP. For
example the BFP620. Ok, it's a bipolar transistor but it sports a
whopping 65GHz ft and is very cheap. Just don't push it much past 2V.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

John Larkin wrote:

On Thu, 10 Jan 2008 21:05:06 GMT, Joerg
notthisjoergsch@removethispacbell.net> wrote:

John Larkin wrote:
On Thu, 10 Jan 2008 17:51:19 GMT, Joerg
notthisjoergsch@removethispacbell.net> wrote:

Jan Panteltje wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?
Usually a transistor that avalanches nicely, a chunk of good coax and
blazingly fast diodes, preferable a matched quad.
I did one with a step-recovery diode impulse generator, feeding a
2-diode sampler. Got 70 ps risetime, roughly 5 GHz, and apparently
good waveform fidelity. The parts cost is tiny, but it's labor
intensive. The timebase and trigger stuff is more work than the
sampler.

The older Tek sampling stuff, the S-series heads and their 7000-series
plugins, are dirt cheap on ebay. But not nearly as nice and
quantitative as the 11801-series stuff.

I doubt you could make a head that would work in an 11801 frame; the
interface is undefined.

A lot in this field is a trade secret or barely defined. And then old
Leroy goes into a nursing home and one day takes that knowledge with him
into the grave.

Same on my main turf (medical ultrasound). Lots of stuff is never
disclosed in detail other than what's required for biocomp testing. To
avoid potential risks some isn't even written down. So if someone would
knock me over the head and walk away with the whole office contents it
wouldn't do them any good.


It would be fun to do a sampling scope/TDR as a USB dongle.

Sure would be fun. But I assume the market size would be rather paltry.
Especially in view of the ever smaller number of young lads who would
know what to actually do with such gear.

If it did TDR, you could sell bundles of them to PCB houses, and to
engineers and QC people who care about trace impedances. Especially if
it were cheap and interfaced to a PC, so it could document pcb test
coupons.

Really? We did lots of RF things in the companies I worked for but never
used much TDR. Ok, it wasn't GHz gear.

I'd design the fast stuff if somebody else handles the USB part and
the PC software. I have a slick deconvolution algorithm that would run
on the pc side and really beautify the TDR response.

Hey, you always want to do the fun stuff ... ;-)

--
Regards, Joerg

http://www.analogconsultants.com/