RF switches...

[Chris Jones]

On 28/02/2022 12:31, jlarkin@highlandsniptechnology.com wrote:

On Mon, 28 Feb 2022 11:20:28 +1100, Chris Jones
lugnut808@spam.yahoo.com> wrote:

On 28/02/2022 02:35, jlarkin@highlandsniptechnology.com wrote:
On Sun, 27 Feb 2022 21:09:48 +1100, Chris Jones
lugnut808@spam.yahoo.com> wrote:

On 27/02/2022 03:16, jlarkin@highlandsniptechnology.com wrote:
On Sat, 26 Feb 2022 13:08:15 +1100, Clifford Heath
no.spam@please.net> wrote:

On 26/2/22 11:03 am, John Larkin wrote:
Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.

ADRF5024 is 100 MHz to 44 GHz, but switches in about 17 ns. The 100
MHz lower signal bw makes no sense.

HMC347 looked pretty good, DC-14 GHz and 10 ns typ, but it\'s gone
obsolete.

Who else makes parts like this?

We\'ve used Skyworks SKY13453 (2-way) and SKY13317 (3-way) but they\'re
only 6GHz. Check their other parts?

And Qorvo of course:
https://www.qorvo.com/products/switches/discrete-switches
https://store.qorvo.com/products/switches/rf-switch?att_4714=1&att_4719=6%2c7

Clifford Heath

Wow, a lot of near-misses.

I\'m amplifying an arbitrary waveform as the seed of a largish laser.
And I want to inject a 100 ps fiducial pulse. We can make a nice
programmable 100 ps gaussian pulse, but can\'t passively mix it with
the arb without wrecking both.

Why? Does each one produce interfering crud when it should produce
nothing, or are you just not able to tolerate the amplitude loss of a
passive resistive combiner?

Amplitide. Neither the arb nor the fiducual generator can make over
about 0.75 volts peak, and the distributed amp needs all of that to
drive the modulator.

Could you increase the output of the fiducial generator somehow? Then a
combiner with unequal resistors could have low loss for the arb.

We\'re using a Micrel laser driver chip, Sy88022. It makes 25 ps edges
and has beautiful linear amplitude control, but is intended to drive a
low impedance laser and won\'t swing even one volt.

Inspired by Leo Bodnar\'s pulse generator, which uses a similar Maxim
chip.


If you don\'t care too much about the shape of the fiducial, there are
probably also some less-broadband-on-one-port combiners that could help
with lower loss for the arb.

The shape really matters. It will be used to test the response of
laser bits downstream. The customer wants a 100 ps gaussian.

If the fiducial generator will drive a low impedance, and if the width
of the pulse is only 100ps, I\'m sure there is some tricky transmission
line transformer way to impose it in series with your arb output and
maintain decent pulse shape. It would take some experimentation though.

Whatever switch you choose, I wonder what amount of glitch gets injected
into the signal output when it switches (charge injection or whatever
you want to call it).

 

[server]

On Mon, 28 Feb 2022 16:55:18 +1100, Chris Jones
<lugnut808@spam.yahoo.com> wrote:

On 28/02/2022 12:31, jlarkin@highlandsniptechnology.com wrote:
On Mon, 28 Feb 2022 11:20:28 +1100, Chris Jones
lugnut808@spam.yahoo.com> wrote:

On 28/02/2022 02:35, jlarkin@highlandsniptechnology.com wrote:
On Sun, 27 Feb 2022 21:09:48 +1100, Chris Jones
lugnut808@spam.yahoo.com> wrote:

On 27/02/2022 03:16, jlarkin@highlandsniptechnology.com wrote:
On Sat, 26 Feb 2022 13:08:15 +1100, Clifford Heath
no.spam@please.net> wrote:

On 26/2/22 11:03 am, John Larkin wrote:
Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.

ADRF5024 is 100 MHz to 44 GHz, but switches in about 17 ns. The 100
MHz lower signal bw makes no sense.

HMC347 looked pretty good, DC-14 GHz and 10 ns typ, but it\'s gone
obsolete.

Who else makes parts like this?

We\'ve used Skyworks SKY13453 (2-way) and SKY13317 (3-way) but they\'re
only 6GHz. Check their other parts?

And Qorvo of course:
https://www.qorvo.com/products/switches/discrete-switches
https://store.qorvo.com/products/switches/rf-switch?att_4714=1&att_4719=6%2c7

Clifford Heath

Wow, a lot of near-misses.

I\'m amplifying an arbitrary waveform as the seed of a largish laser.
And I want to inject a 100 ps fiducial pulse. We can make a nice
programmable 100 ps gaussian pulse, but can\'t passively mix it with
the arb without wrecking both.

Why? Does each one produce interfering crud when it should produce
nothing, or are you just not able to tolerate the amplitude loss of a
passive resistive combiner?

Amplitide. Neither the arb nor the fiducual generator can make over
about 0.75 volts peak, and the distributed amp needs all of that to
drive the modulator.

Could you increase the output of the fiducial generator somehow? Then a
combiner with unequal resistors could have low loss for the arb.

We\'re using a Micrel laser driver chip, Sy88022. It makes 25 ps edges
and has beautiful linear amplitude control, but is intended to drive a
low impedance laser and won\'t swing even one volt.

Inspired by Leo Bodnar\'s pulse generator, which uses a similar Maxim
chip.


If you don\'t care too much about the shape of the fiducial, there are
probably also some less-broadband-on-one-port combiners that could help
with lower loss for the arb.

The shape really matters. It will be used to test the response of
laser bits downstream. The customer wants a 100 ps gaussian.

If the fiducial generator will drive a low impedance, and if the width
of the pulse is only 100ps, I\'m sure there is some tricky transmission
line transformer way to impose it in series with your arb output and
maintain decent pulse shape. It would take some experimentation though.

Whatever switch you choose, I wonder what amount of glitch gets injected
into the signal output when it switches (charge injection or whatever
you want to call it).

One would think that would be specified on the data sheet of an analog
switch. It isn\'t.

I guess that RF people don\'t have oscilloscopes.



--

I yam what I yam - Popeye

 

[server]

On Sun, 27 Feb 2022 21:46:24 -0800 (PST), \"John Miles, KE5FX\"
<jmiles@gmail.com> wrote:

On Friday, February 25, 2022 at 4:03:45 PM UTC-8, John Larkin wrote:
Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.

PE42525, maybe. 9 kHz-60 GHz, SPDT, 8-12 ns switching time to
10%/90%, 48-60 ns settling time to 0.05 dB.

I\'d be surprised if you find anything faster than that. PSemi makes
fantastic stuff (at least, when you can buy it.)

-- john, KE5FX

Interesting, but bare die. It reminds me of some of the Hittite parts:
no power pins. And no capacitance spec on the control pins.





--

I yam what I yam - Popeye

 

[mixed nuts]

On 2/25/2022 19:03, John Larkin wrote:

Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.

ADRF5024 is 100 MHz to 44 GHz, but switches in about 17 ns. The 100
MHz lower signal bw makes no sense.

HMC347 looked pretty good, DC-14 GHz and 10 ns typ, but it\'s gone
obsolete.

Who else makes parts like this?

Start here:

Warren, W. S. (1987).
Effects of Pulse Shaping in Laser Spectroscopy
Laser Applications to Chemical Dynamics.
doi:10.1117/12.966903

WSW is still active - Duke U.


--
Grizzly H.

 

[Simon S Aysdie]

On Friday, February 25, 2022 at 4:03:45 PM UTC-8, John Larkin wrote:

Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.

ADRF5024 is 100 MHz to 44 GHz, but switches in about 17 ns. The 100
MHz lower signal bw makes no sense.

HMC347 looked pretty good, DC-14 GHz and 10 ns typ, but it\'s gone
obsolete.

Who else makes parts like this?

https://www.psemi.com/pdf/datasheets/pe42525ds.pdf

and other switches.

I\'d check Macom too. We\'ve been designing some of our own lately.

Just a note: there is a difference between amplitude settling and switching speed. I think you do care about switching speed.

 

[Skittles]

On Mon, 28 Feb 2022 16:39:34 -0500, mixed nuts
<melopsitticus@undulatus.budgie> wrote:

On 2/25/2022 19:03, John Larkin wrote:
Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.

ADRF5024 is 100 MHz to 44 GHz, but switches in about 17 ns. The 100
MHz lower signal bw makes no sense.

HMC347 looked pretty good, DC-14 GHz and 10 ns typ, but it\'s gone
obsolete.

Who else makes parts like this?

Start here:

Warren, W. S. (1987).
Effects of Pulse Shaping in Laser Spectroscopy
Laser Applications to Chemical Dynamics.
doi:10.1117/12.966903

WSW is still active - Duke U.

It amazes me that so many people spec RF switches without asking the
power of the signal to be switched. Pretty fundamental.

What is the typical coherence length for light in chemical solutions?


Skittles

 

[server]

On Tue, 1 Mar 2022 20:10:05 -0800 (PST), Simon S Aysdie
<gwhite@ti.com> wrote:

On Friday, February 25, 2022 at 4:03:45 PM UTC-8, John Larkin wrote:
Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.

ADRF5024 is 100 MHz to 44 GHz, but switches in about 17 ns. The 100
MHz lower signal bw makes no sense.

HMC347 looked pretty good, DC-14 GHz and 10 ns typ, but it\'s gone
obsolete.

Who else makes parts like this?

https://www.psemi.com/pdf/datasheets/pe42525ds.pdf

and other switches.

I\'d check Macom too. We\'ve been designing some of our own lately.

Just a note: there is a difference between amplitude settling and switching speed. I think you do care about switching speed.

I\'m working with short, shaped pulses, so I want the switch to have
good pulse fidelity within some fast time of switching.

ADRF5024 looks good. Its gross switching happens in under 10 ns and is
pretty clean. In fine RF tradition, it\'s underspecified and specs are
basically dishonest.



--

I yam what I yam - Popeye

 

[Skittle]

On Tue, 08 Mar 2022 07:59:10 -0800, jlarkin@highlandsniptechnology.com
wrote:

On Tue, 1 Mar 2022 20:10:05 -0800 (PST), Simon S Aysdie
gwhite@ti.com> wrote:

On Friday, February 25, 2022 at 4:03:45 PM UTC-8, John Larkin wrote:
Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.

ADRF5024 is 100 MHz to 44 GHz, but switches in about 17 ns. The 100
MHz lower signal bw makes no sense.

HMC347 looked pretty good, DC-14 GHz and 10 ns typ, but it\'s gone
obsolete.

Who else makes parts like this?

https://www.psemi.com/pdf/datasheets/pe42525ds.pdf

and other switches.

I\'d check Macom too. We\'ve been designing some of our own lately.

Just a note: there is a difference between amplitude settling and switching speed. I think you do care about switching speed.


I\'m working with short, shaped pulses, so I want the switch to have
good pulse fidelity within some fast time of switching.

ADRF5024 looks good. Its gross switching happens in under 10 ns and is
pretty clean. In fine RF tradition, it\'s underspecified and specs are
basically dishonest.

You may want to look the the switch through a TDR (Time domain
reflectomter). That will give you the best measurement for switch\'s
ability to maintain pulse fidelity.

Skittles

 

[server]

On Tue, 08 Mar 2022 09:04:16 -0700, Skittles<Skittles@nowhere8.org>
wrote:

On Tue, 08 Mar 2022 07:59:10 -0800, jlarkin@highlandsniptechnology.com
wrote:

On Tue, 1 Mar 2022 20:10:05 -0800 (PST), Simon S Aysdie
gwhite@ti.com> wrote:

On Friday, February 25, 2022 at 4:03:45 PM UTC-8, John Larkin wrote:
Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.

ADRF5024 is 100 MHz to 44 GHz, but switches in about 17 ns. The 100
MHz lower signal bw makes no sense.

HMC347 looked pretty good, DC-14 GHz and 10 ns typ, but it\'s gone
obsolete.

Who else makes parts like this?

https://www.psemi.com/pdf/datasheets/pe42525ds.pdf

and other switches.

I\'d check Macom too. We\'ve been designing some of our own lately.

Just a note: there is a difference between amplitude settling and switching speed. I think you do care about switching speed.


I\'m working with short, shaped pulses, so I want the switch to have
good pulse fidelity within some fast time of switching.

ADRF5024 looks good. Its gross switching happens in under 10 ns and is
pretty clean. In fine RF tradition, it\'s underspecified and specs are
basically dishonest.


You may want to look the the switch through a TDR (Time domain
reflectomter). That will give you the best measurement for switch\'s
ability to maintain pulse fidelity.

Skittles

We\'ve been testing a number of RF switches with pulse generators and
TDR. It has been interesting.

Several of the eval boards have the no-solder screw-on microwave
connectors. The eval boards are free or less if you account for those.





--

I yam what I yam - Popeye

 

[mixed nuts]

On 3/8/2022 09:49, Skittles wrote:

On Mon, 28 Feb 2022 16:39:34 -0500, mixed nuts
melopsitticus@undulatus.budgie> wrote:

On 2/25/2022 19:03, John Larkin wrote:
Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.

ADRF5024 is 100 MHz to 44 GHz, but switches in about 17 ns. The 100
MHz lower signal bw makes no sense.

HMC347 looked pretty good, DC-14 GHz and 10 ns typ, but it\'s gone
obsolete.

Who else makes parts like this?

Start here:

Warren, W. S. (1987).
Effects of Pulse Shaping in Laser Spectroscopy
Laser Applications to Chemical Dynamics.
doi:10.1117/12.966903

WSW is still active - Duke U.


It amazes me that so many people spec RF switches without asking the
power of the signal to be switched. Pretty fundamental.

What is the typical coherence length for light in chemical solutions?

10^10 light years for dilute homogeneous solutions, <1 um for dense
anisotropic dispersive solutions.

--
Grizzly H.

 

[John Miles, KE5FX]

On Monday, February 28, 2022 at 2:33:54 AM UTC-8, jla...@highlandsniptechnology.com wrote:

Interesting, but bare die. It reminds me of some of the Hittite parts:
no power pins. And no capacitance spec on the control pins.

I see they now have a packaged version:

https://www.psemi.com/products/rf-switches/broadband-rf-switches/pe42546

Only rated for 45 GHz, though, so there\'s that. No actual data yet other than the
\"product brief.\" Their parts generally do what they say, though.

-- john, KE5FX

 

[server]

On Tue, 08 Mar 2022 21:09:03 -0700, Skittles<Skittles@nowhere8.org>
wrote:

On Tue, 08 Mar 2022 08:58:31 -0800, jlarkin@highlandsniptechnology.com
wrote:

On Tue, 08 Mar 2022 09:04:16 -0700, Skittles<Skittles@nowhere8.org
wrote:

On Tue, 08 Mar 2022 07:59:10 -0800, jlarkin@highlandsniptechnology.com
wrote:

On Tue, 1 Mar 2022 20:10:05 -0800 (PST), Simon S Aysdie
gwhite@ti.com> wrote:

On Friday, February 25, 2022 at 4:03:45 PM UTC-8, John Larkin wrote:
Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.

ADRF5024 is 100 MHz to 44 GHz, but switches in about 17 ns. The 100
MHz lower signal bw makes no sense.

HMC347 looked pretty good, DC-14 GHz and 10 ns typ, but it\'s gone
obsolete.

Who else makes parts like this?

https://www.psemi.com/pdf/datasheets/pe42525ds.pdf

and other switches.

I\'d check Macom too. We\'ve been designing some of our own lately.

Just a note: there is a difference between amplitude settling and switching speed. I think you do care about switching speed.


I\'m working with short, shaped pulses, so I want the switch to have
good pulse fidelity within some fast time of switching.

ADRF5024 looks good. Its gross switching happens in under 10 ns and is
pretty clean. In fine RF tradition, it\'s underspecified and specs are
basically dishonest.


You may want to look the the switch through a TDR (Time domain
reflectomter). That will give you the best measurement for switch\'s
ability to maintain pulse fidelity.

Skittles

We\'ve been testing a number of RF switches with pulse generators and
TDR. It has been interesting.

Several of the eval boards have the no-solder screw-on microwave
connectors. The eval boards are free or less if you account for those.


What kind of transmission line are you running into the switches?
Sometimes that can really affect your measurements.

The eval boards usually have CPW

https://www.dropbox.com/s/rbo4mzo640z43t6/ADRF5024-EVALZTOP-web.png?raw=1

which they can do if all you need is one tiny part on a relatively
giant board.

Our boards are most always microstrip, because we need to pack a lot
of parts onto a small board.

https://www.dropbox.com/s/bb16beiwymbu28a/T502A.jpg?raw=1

For instance if you are running coplanar or microstrip and you have
some components from the line to ground, they should be split equally
to both sides of the line. Say your circuit had 100 ohm to ground, it
should be 2 each 200 ohm to ground on both edges of the line so the
currents split evenly. Make sure the ground current follows the same
path as the signal, each being in different planes.

In real life, we need to jam parts very close together, and that
dominates layout.

Things that go to ground usually do that to a big layer 1 ground pour.
Vias down to layer 2 have too much personality.

We don\'t think much about \"return currents.\" Actually, not at all.






--

I yam what I yam - Popeye

 

[server]

Anthony William Sloman <bill.sloman@ieee.org> wrote in
news:6e6c0cc9-daf7-416d-b7c8-e3b5565174cbn@googlegroups.com:

I have tried to get John Larkin to think about (buried)
strip-lines, which you can bury inside multi-layer boards. Unlike
structures on the surface, they can be non-dispersive. There\'s no
way to suggest this in away that sounds flattering, so John isn\'t
interested.

I have done some stripline designs. Before I would move forward with
your idea, which sounds good to me, btw, I would run it past my boss of
over 30 years, and he is one of the top RF engineers on the planet
(was).

 

[server]

On Wed, 9 Mar 2022 10:16:16 -0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Anthony William Sloman <bill.sloman@ieee.org> wrote in
news:6e6c0cc9-daf7-416d-b7c8-e3b5565174cbn@googlegroups.com:

I have tried to get John Larkin to think about (buried)
strip-lines, which you can bury inside multi-layer boards. Unlike
structures on the surface, they can be non-dispersive. There\'s no
way to suggest this in away that sounds flattering, so John isn\'t
interested.

I have done some stripline designs. Before I would move forward with
your idea, which sounds good to me, btw, I would run it past my boss of
over 30 years, and he is one of the top RF engineers on the planet
(was).

Parts mount on the surface. Stripline traces are inherently several
layers down. The connection to a stripline trace involves at least two
vias. Vias are deadly for really fast signals.

Sloman pontificates and insults and hasn\'t designed actual electronics
in decades, and what he did decades ago sounds mostly like failures.

We do a lot of multilayer test boards and real production boards.
Experiment is a good check on guesswork theories.

And we\'re not designing RF, we\'re doing picosecond time domain stuff.
Working around 10 GHz is different from DC-to-10GHz. We measure signal
fidelity in PPM, not dB.

This drives the \"slicer\" section of a 2-stage e/o modulator:

https://www.dropbox.com/s/34j6pjg31qie2le/T503_FA3.jpg?raw=1

We\'ve improved the monitor pickoff on the current rev. This fast stuff
depends a lot on instinct and experiment, mostly because we don\'t have
good, or usually any, time-domain part models. It\'s amazing how much
we don\'t know about the parts we use.



--

I yam what I yam - Popeye

 

[John S]

On 3/9/2022 9:10 AM, jlarkin@highlandsniptechnology.com wrote:

On Wed, 9 Mar 2022 10:16:16 -0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Anthony William Sloman <bill.sloman@ieee.org> wrote in
news:6e6c0cc9-daf7-416d-b7c8-e3b5565174cbn@googlegroups.com:

I have tried to get John Larkin to think about (buried)
strip-lines, which you can bury inside multi-layer boards. Unlike
structures on the surface, they can be non-dispersive. There\'s no
way to suggest this in away that sounds flattering, so John isn\'t
interested.

I have done some stripline designs. Before I would move forward with
your idea, which sounds good to me, btw, I would run it past my boss of
over 30 years, and he is one of the top RF engineers on the planet
(was).

Parts mount on the surface. Stripline traces are inherently several
layers down. The connection to a stripline trace involves at least two
vias. Vias are deadly for really fast signals.

In what way are they deadly, John? Would the result of being deadly show
up in a frequency domain test?

 

[John Larkin]

On Wed, 9 Mar 2022 13:12:32 -0600, John S <Sophi.2@invalid.org> wrote:

On 3/9/2022 9:10 AM, jlarkin@highlandsniptechnology.com wrote:
On Wed, 9 Mar 2022 10:16:16 -0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Anthony William Sloman <bill.sloman@ieee.org> wrote in
news:6e6c0cc9-daf7-416d-b7c8-e3b5565174cbn@googlegroups.com:

I have tried to get John Larkin to think about (buried)
strip-lines, which you can bury inside multi-layer boards. Unlike
structures on the surface, they can be non-dispersive. There\'s no
way to suggest this in away that sounds flattering, so John isn\'t
interested.

I have done some stripline designs. Before I would move forward with
your idea, which sounds good to me, btw, I would run it past my boss of
over 30 years, and he is one of the top RF engineers on the planet
(was).

Parts mount on the surface. Stripline traces are inherently several
layers down. The connection to a stripline trace involves at least two
vias. Vias are deadly for really fast signals.


In what way are they deadly, John? Would the result of being deadly show
up in a frequency domain test?

Time and (wideband) frequency domain tests are nearly interchangeable.
In a fast time domain test, a via typically looks like a capacitor.
Vias can be carefully tuned to match a trace impedance, but a thru via
overshoots the transition to a microstrip and makes a nasty little
stub with a pad on both ends. Blind vias are better but run up board
cost.

We usually keep our fast connections microstrip on layer 1, with
ground plane as layer 2, and run power planes and slow stuff on layers
below.

Ground vias are inductive, so we have big ground pours on layer 1 with
a lot of vias down to the layer 2 ground plane.

Layout becomes a puzzle like doing single-sided boards in ancient
times.

\"RF\" is usually narrowband, so parasitics can be tuned out.

--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon

 

[Anthony William Sloman]

On Thursday, March 10, 2022 at 2:10:27 AM UTC+11, jla...@highlandsniptechnology.com wrote:

On Wed, 9 Mar 2022 10:16:16 -0000 (UTC), DecadentLinux...@decadence.org wrote:
Anthony William Sloman <bill....@ieee.org> wrote in news:6e6c0cc9-daf7-416d...@googlegroups.com:

I have tried to get John Larkin to think about (buried)
strip-lines, which you can bury inside multi-layer boards. Unlike
structures on the surface, they can be non-dispersive. There\'s no
way to suggest this in away that sounds flattering, so John isn\'t
interested.

I have done some stripline designs. Before I would move forward with
your idea, which sounds good to me, btw, I would run it past my boss of
over 30 years, and he is one of the top RF engineers on the planet
(was).

Parts mount on the surface. Stripline traces are inherently several
layers down. The connection to a stripline trace involves at least two
vias. Vias are deadly for really fast signals.

If \"designed\" - which is to say fudged - buy John Larkin. It\'s extra inductance which can be neurtalised.

> Sloman pontificates and insults and hasn\'t designed actual electronics in decades, and what he did decades ago sounds mostly like failures.

Cambridge Instruments fast stuff was mostly 1988 to 1991, and was a technical success and a commercial failure.
I did at bit more at Nijmegen University around 1997. I cleaned up an old nanosecond pulse generator by replacing some of the TTL with ECLinPS, and got rid of a nasty sub-nanosecond jitter, which prompted the user to get us to design an ECLinPS-based replacement. We spent about a year doing the detailed design of the hardware and the software to run it, but the user ran out of funding at the point when we were starting on the layout. Not a successful development, but not a technical failure either.

We do a lot of multilayer test boards and real production boards.
Experiment is a good check on guesswork theories.

The theories aren\'t guesswork, but experiment is a lot cheaper than simulations that are detailed enough to be all that reliable.

> And we\'re not designing RF, we\'re doing picosecond time domain stuff.

And so was I.

Working around 10 GHz is different from DC-to-10GHz. We measure signal fidelity in PPM, not dB.

This drives the \"slicer\" section of a 2-stage e/o modulator:

https://www.dropbox.com/s/34j6pjg31qie2le/T503_FA3.jpg?raw=1

We were producing 500psec wide pulses from about 1985. Your scope image is of a 4nsec wide pulse.

We\'ve improved the monitor pickoff on the current rev. This fast stuff
depends a lot on instinct and experiment, mostly because we don\'t have
good, or usually any, time-domain part models. It\'s amazing how much
we don\'t know about the parts we use.

And don\'t seem to be able to find out. Models are what you put together to fit experimental data. Manufacturers often do it for you.

LTSpice frequently gives access to some manufacturers part models, but when I\'ve used the BFR92 I\'ve had to import the NXP Gummel Poon model myself.

https://www.nxp.com/downloads/en/spice-model/spice_BFR92A.prm

It has shown up in ,asc files I\'ve posted here.

--
Bill Sloman, Sydney