non-pipelined fast ADC...

[whit3rd]

On Sunday, August 30, 2020 at 9:11:07 AM UTC-7, jla...@highlandsniptechnology.com wrote:

I start an LC oscillator when I get a trigger, and use it to time out
delays. The ADC is clocked from an OCXO and observes the waveform of
the triggered LC oscillator, and I close a loop to lock the LC to the
XO. Actually, the LC frequency is whatever it wants to be. The math
gets ugly.

I\'m thinking along those same lines. If I can (quickly!) measure the
phase angle between my XO and my triggered oscillator, I can seize the
initial phase offset and close a loop on that. ...

My triggered LC oscillator is great for a couple of microseconds, but
is piling up drift and jitter. It needs to be locked to a good XO
long-term.

This makes no sense; if you lock it to the XO with any variant of phase-locking,
it\'s NO LONGER phase-locked to the trigger event, and the measurement is worthless.
Just cancel the trigger-caused start phase against an XO-caused start phase,
and ignore the absolute frequency of the LC entirely (unless you think it drifts
enough in a few milliseconds to matter).

 

[Phil Hobbs]

On 2020-08-30 17:08, whit3rd wrote:

On Sunday, August 30, 2020 at 9:11:07 AM UTC-7, jla...@highlandsniptechnology.com wrote:

I start an LC oscillator when I get a trigger, and use it to time out
delays. The ADC is clocked from an OCXO and observes the waveform of
the triggered LC oscillator, and I close a loop to lock the LC to the
XO. Actually, the LC frequency is whatever it wants to be. The math
gets ugly.

I\'m thinking along those same lines. If I can (quickly!) measure the
phase angle between my XO and my triggered oscillator, I can seize the
initial phase offset and close a loop on that. ...

My triggered LC oscillator is great for a couple of microseconds, but
is piling up drift and jitter. It needs to be locked to a good XO
long-term.

This makes no sense; if you lock it to the XO with any variant of phase-locking,
it\'s NO LONGER phase-locked to the trigger event, and the measurement is worthless.
Just cancel the trigger-caused start phase against an XO-caused start phase,
and ignore the absolute frequency of the LC entirely (unless you think it drifts
enough in a few milliseconds to matter).

You\'ve never actually used a state-of-the-art digital delay generator, I
gather. Good ones have jitter down around 10 ps over fairly long
periods. Even the SRS DG535 I bought ~25 years ago had jitter less than
100 ps, and newer ones are much better.

The idea that an LC oscillator could hold the necessary phase accuracy
for milliseconds is ridiculous.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Phil Hobbs]

On 2020-08-25 23:09, Ricketty C wrote:

On Tuesday, August 25, 2020 at 2:34:31 PM UTC-4, John Larkin wrote:
Does anybody know of one? I\'d like to digitize 6 bits or so, really
fast. Most fast ADCs take 3 or 4 clocks to process the data. Even 4
bits might work.

Classic \"flash\" ADCs were fast, but needed 2^N comparators.

If you want a really fast 6 bit converter look to see what they were selling 20 years ago.

I\'m actually surprised they don\'t still make them in 6 bits. I thought they mostly went to the complicated architectures to increase the resolution, but I guess the logic can be run faster with pipelining. There\'s FAST and there\'s DAMN FAST. That was actually terms used in a National data book if I remember correctly... for buffers I believe.

The LH0033 and LH0063. I asked Bob Pease why their 1990 databook
changed it to \"fast and very fast\", and he said the edict came right
from Charlie Sporck.


Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Chris]

On 08/28/20 17:47, Phil Hobbs wrote:

On 2020-08-26 14:47, Chris wrote:
On 08/26/20 19:40, piglet wrote:
On 26/08/2020 5:58 pm, Gerhard Hoffmann wrote:
Am 26.08.20 um 18:29 schrieb Chris:


The older high end HP spectrum analysers, the 8566 and 8568 did that
as well. The marketing blurb called it lock and roll, locking the
LO at start of sweep, then free running it open loop for the rest
of the sweep. Allowed them to have a stable 10Hz resolution bw and
1KHz span at Ghz, in the late 1970\'s.

I think what I was really saying was, was if the solution gets too
complex, it maybe the wrong approach ...

IIRC, there was an article in the HP Journal about this.
I think I have it on paper somewhere, but HP Journal
is probably searchable somewhere.

Cheers, Gerhard

This one?
http://hparchive.com/Journals/HPJ-1978-06.pdf

piglet


I think i\'ve seen that.Amazing bit of kit for it\'s time. HP really
were at the peak of their game back then with tech prowess few,
if any could match. Much of it still in use today.

Last catalog price for the 8566, iirc, was 78,000 usd and yet,
they sold bucketloads of them...

Back in 1982, when I was working in satcom, we had a reasonably new
Ailtech 757 (iirc). It was a manually-tuned gizmo that drifted around a
bit before it warmed up.

Then we got a swoopy new HP 8566A, later upgraded to a B. I was hooked.
I had one for awhile at IBM, and about 6 years I bought a used one on
eBay when I needed more top end than my previous 8568B. Its close-in
phase noise is remarkably low on account of its YIG-tuned sweep oscillator.

Its main drawback is that you can have the RF or microwave band
displayed, but not both at once. Still, for 2 cents on the dollar one
really can\'t complain too loudly.

Cheers

Phil Hobbs

Most of the older HP analysers drifted a lot and needed a warmup period
of anything up to an hour before they were fit to use. Both the 8566 and
8568 were a step function improvement, in that they were ready for use
almost right away, Both use the same display section and the 10Hz
resolution bw option is makes them great for close in pjhase noise checking.

Have one of each here, came from an rf / emc lab amd must have been on
24/7. Both display sections had a fuzzy tube, but got on to the John
Miles site and restored them back to sharp focus. Don\'t know how long
they will last, but only used occasionally, so not a problem. Still a
lot of them in use apparently, probably because they have a spec that\'s
difficult to match even now...

Chris

 

[Phil Hobbs]

On 2020-08-30 19:17, Chris wrote:

On 08/28/20 17:47, Phil Hobbs wrote:
On 2020-08-26 14:47, Chris wrote:
On 08/26/20 19:40, piglet wrote:
On 26/08/2020 5:58 pm, Gerhard Hoffmann wrote:
Am 26.08.20 um 18:29 schrieb Chris:


The older high end HP spectrum analysers, the 8566 and 8568 did that
as well.  The marketing blurb called it lock and roll, locking the
LO at start of sweep, then free running it open loop for the rest
of the sweep. Allowed them to have a stable 10Hz resolution bw and
1KHz span at Ghz, in the late 1970\'s.

I think what I was really saying was, was if the solution gets too
complex, it maybe the wrong approach ...

IIRC, there was an article in the HP Journal about this.
I think I have it on paper somewhere, but HP Journal
is probably searchable somewhere.

Cheers, Gerhard

This one?
http://hparchive.com/Journals/HPJ-1978-06.pdf

piglet


I think i\'ve seen that.Amazing bit of kit for it\'s time. HP really
were at the peak of their game back then with tech prowess few,
if any could match. Much of it still in use today.

Last catalog price for the 8566, iirc, was 78,000 usd and yet,
they sold bucketloads of them...

Back in 1982, when I was working in satcom, we had a reasonably new
Ailtech 757 (iirc). It was a manually-tuned gizmo that drifted around a
bit before it warmed up.

Then we got a swoopy new HP 8566A, later upgraded to a B. I was hooked.
I had one for awhile at IBM, and about 6 years I bought a used one on
eBay when I needed more top end than my previous 8568B. Its close-in
phase noise is remarkably low on account of its YIG-tuned sweep
oscillator.

Its main drawback is that you can have the RF or microwave band
displayed, but not both at once. Still, for 2 cents on the dollar one
really can\'t complain too loudly.

Cheers

Phil Hobbs


Most of the older HP analysers drifted a lot and needed a warmup period
of anything up to an hour before they were fit to use. Both the 8566 and
8568 were a step function improvement, in that they were ready for use
almost right away, Both use the same display section and the 10Hz
resolution bw option is makes them great for close in pjhase noise
checking.

Have one of each here, came from an rf / emc lab amd must have been on
24/7. Both display sections had a fuzzy tube, but got on to the John
Miles site and restored them back to sharp focus. Don\'t know how long
they will last, but only used occasionally, so not a problem. Still a
lot of them in use apparently, probably because they have a spec that\'s
difficult to match even now...

Chris

And getting harder. The SDR-based analyzers are so cheap that they\'re
taking over the market.

Cheers

Phil \"YIG-tuned forever\" Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[server]

On Sun, 30 Aug 2020 19:06:41 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-08-30 17:08, whit3rd wrote:
On Sunday, August 30, 2020 at 9:11:07 AM UTC-7, jla...@highlandsniptechnology.com wrote:

I start an LC oscillator when I get a trigger, and use it to time out
delays. The ADC is clocked from an OCXO and observes the waveform of
the triggered LC oscillator, and I close a loop to lock the LC to the
XO. Actually, the LC frequency is whatever it wants to be. The math
gets ugly.

I\'m thinking along those same lines. If I can (quickly!) measure the
phase angle between my XO and my triggered oscillator, I can seize the
initial phase offset and close a loop on that. ...

My triggered LC oscillator is great for a couple of microseconds, but
is piling up drift and jitter. It needs to be locked to a good XO
long-term.

This makes no sense; if you lock it to the XO with any variant of phase-locking,
it\'s NO LONGER phase-locked to the trigger event, and the measurement is worthless.
Just cancel the trigger-caused start phase against an XO-caused start phase,
and ignore the absolute frequency of the LC entirely (unless you think it drifts
enough in a few milliseconds to matter).


You\'ve never actually used a state-of-the-art digital delay generator, I
gather. Good ones have jitter down around 10 ps over fairly long
periods. Even the SRS DG535 I bought ~25 years ago had jitter less than
100 ps, and newer ones are much better.

The idea that an LC oscillator could hold the necessary phase accuracy
for milliseconds is ridiculous.

I did one OEM delay generator that used an unlocked, triggered coaxial
ceramic resonator oscillator. It was better than an open-loop LC, but
not good enough.

Cheers

Phil Hobbs

The SRS boxes use the XO to count out time delays. But in the
front-end, they measure the delta-T between the external trigger and
the local XO clock, and then subtract that out of the back-end pulses.
It works sort of OK, but their boxes are user-interface horrors. The
DG645 was designed by a guy that I fired.

https://www.dropbox.com/s/t7uo7cnybgk74e4/Top_1.jpg?raw=1

https://www.dropbox.com/s/4fmf86rrpne428m/DG645_Connectors.JPG?raw=1

https://www.dropbox.com/s/szg1rzqrp7ut96e/DG645_7-segment.jpg?raw=1

SRS loves to spell out messages in 7-segment. I always thought it
would be fun to write a novel in 7-seg text.

The French thing apparently uses SERDES blocks in an FPGA. I think the
idea is to just run the digital counter stuff really fast. RMS jitter
is clock period divided by the square root of 12, which seems magical
to me.

We\'ll have a new DDG soon.





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[server]

On Sun, 30 Aug 2020 19:28:23 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-08-30 19:17, Chris wrote:
On 08/28/20 17:47, Phil Hobbs wrote:
On 2020-08-26 14:47, Chris wrote:
On 08/26/20 19:40, piglet wrote:
On 26/08/2020 5:58 pm, Gerhard Hoffmann wrote:
Am 26.08.20 um 18:29 schrieb Chris:


The older high end HP spectrum analysers, the 8566 and 8568 did that
as well.  The marketing blurb called it lock and roll, locking the
LO at start of sweep, then free running it open loop for the rest
of the sweep. Allowed them to have a stable 10Hz resolution bw and
1KHz span at Ghz, in the late 1970\'s.

I think what I was really saying was, was if the solution gets too
complex, it maybe the wrong approach ...

IIRC, there was an article in the HP Journal about this.
I think I have it on paper somewhere, but HP Journal
is probably searchable somewhere.

Cheers, Gerhard

This one?
http://hparchive.com/Journals/HPJ-1978-06.pdf

piglet


I think i\'ve seen that.Amazing bit of kit for it\'s time. HP really
were at the peak of their game back then with tech prowess few,
if any could match. Much of it still in use today.

Last catalog price for the 8566, iirc, was 78,000 usd and yet,
they sold bucketloads of them...

Back in 1982, when I was working in satcom, we had a reasonably new
Ailtech 757 (iirc). It was a manually-tuned gizmo that drifted around a
bit before it warmed up.

Then we got a swoopy new HP 8566A, later upgraded to a B. I was hooked.
I had one for awhile at IBM, and about 6 years I bought a used one on
eBay when I needed more top end than my previous 8568B. Its close-in
phase noise is remarkably low on account of its YIG-tuned sweep
oscillator.

Its main drawback is that you can have the RF or microwave band
displayed, but not both at once. Still, for 2 cents on the dollar one
really can\'t complain too loudly.

Cheers

Phil Hobbs


Most of the older HP analysers drifted a lot and needed a warmup period
of anything up to an hour before they were fit to use. Both the 8566 and
8568 were a step function improvement, in that they were ready for use
almost right away, Both use the same display section and the 10Hz
resolution bw option is makes them great for close in pjhase noise
checking.

Have one of each here, came from an rf / emc lab amd must have been on
24/7. Both display sections had a fuzzy tube, but got on to the John
Miles site and restored them back to sharp focus. Don\'t know how long
they will last, but only used occasionally, so not a problem. Still a
lot of them in use apparently, probably because they have a spec that\'s
difficult to match even now...

Chris


And getting harder. The SDR-based analyzers are so cheap that they\'re
taking over the market.

Cheers

Phil \"YIG-tuned forever\" Hobbs

Isn\'t a YIG frequency determined by the mag field? How can that be
controlled to PPB precision?



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[Chris]

On 08/31/20 00:06, Phil Hobbs wrote:

On 2020-08-30 17:08, whit3rd wrote:
On Sunday, August 30, 2020 at 9:11:07 AM UTC-7,
jla...@highlandsniptechnology.com wrote:

I start an LC oscillator when I get a trigger, and use it to time
out
delays. The ADC is clocked from an OCXO and observes the waveform of
the triggered LC oscillator, and I close a loop to lock the LC to
the
XO. Actually, the LC frequency is whatever it wants to be. The math
gets ugly.

I\'m thinking along those same lines. If I can (quickly!) measure the
phase angle between my XO and my triggered oscillator, I can seize the
initial phase offset and close a loop on that. ...

My triggered LC oscillator is great for a couple of microseconds, but
is piling up drift and jitter. It needs to be locked to a good XO
long-term.

This makes no sense; if you lock it to the XO with any variant of
phase-locking,
it\'s NO LONGER phase-locked to the trigger event, and the measurement
is worthless.
Just cancel the trigger-caused start phase against an XO-caused start
phase,
and ignore the absolute frequency of the LC entirely (unless you think
it drifts
enough in a few milliseconds to matter).


You\'ve never actually used a state-of-the-art digital delay generator, I
gather. Good ones have jitter down around 10 ps over fairly long
periods. Even the SRS DG535 I bought ~25 years ago had jitter less than
100 ps, and newer ones are much better.

The idea that an LC oscillator could hold the necessary phase accuracy
for milliseconds is ridiculous.

Cheers

Phil Hobbs

The od HP5359a time synthesiser of similar vintage, should do that as
well...

Chris

 

[Phil Hobbs]

On 2020-08-30 19:37, jlarkin@highlandsniptechnology.com wrote:

On Sun, 30 Aug 2020 19:06:41 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-08-30 17:08, whit3rd wrote:
On Sunday, August 30, 2020 at 9:11:07 AM UTC-7, jla...@highlandsniptechnology.com wrote:

I start an LC oscillator when I get a trigger, and use it to time out
delays. The ADC is clocked from an OCXO and observes the waveform of
the triggered LC oscillator, and I close a loop to lock the LC to the
XO. Actually, the LC frequency is whatever it wants to be. The math
gets ugly.

I\'m thinking along those same lines. If I can (quickly!) measure the
phase angle between my XO and my triggered oscillator, I can seize the
initial phase offset and close a loop on that. ...

My triggered LC oscillator is great for a couple of microseconds, but
is piling up drift and jitter. It needs to be locked to a good XO
long-term.

This makes no sense; if you lock it to the XO with any variant of phase-locking,
it\'s NO LONGER phase-locked to the trigger event, and the measurement is worthless.
Just cancel the trigger-caused start phase against an XO-caused start phase,
and ignore the absolute frequency of the LC entirely (unless you think it drifts
enough in a few milliseconds to matter).


You\'ve never actually used a state-of-the-art digital delay generator, I
gather. Good ones have jitter down around 10 ps over fairly long
periods. Even the SRS DG535 I bought ~25 years ago had jitter less than
100 ps, and newer ones are much better.

The idea that an LC oscillator could hold the necessary phase accuracy
for milliseconds is ridiculous.

I did one OEM delay generator that used an unlocked, triggered coaxial
ceramic resonator oscillator. It was better than an open-loop LC, but
not good enough.



Cheers

Phil Hobbs

The SRS boxes use the XO to count out time delays. But in the
front-end, they measure the delta-T between the external trigger and
the local XO clock, and then subtract that out of the back-end pulses.
It works sort of OK, but their boxes are user-interface horrors. The
DG645 was designed by a guy that I fired.

https://www.dropbox.com/s/t7uo7cnybgk74e4/Top_1.jpg?raw=1

https://www.dropbox.com/s/4fmf86rrpne428m/DG645_Connectors.JPG?raw=1

https://www.dropbox.com/s/szg1rzqrp7ut96e/DG645_7-segment.jpg?raw=1

SRS loves to spell out messages in 7-segment. I always thought it
would be fun to write a novel in 7-seg text.

IT UAS A OARK And 5TOrnn4 nI6HT....

The French thing apparently uses SERDES blocks in an FPGA. I think the
idea is to just run the digital counter stuff really fast. RMS jitter
is clock period divided by the square root of 12, which seems magical
to me.

That\'s the normal RMS uncertainty of an ideal digitizer.

We\'ll have a new DDG soon.

Looking forward to seeing it!

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Phil Hobbs]

On 2020-08-30 19:55, Chris wrote:

On 08/31/20 00:06, Phil Hobbs wrote:
On 2020-08-30 17:08, whit3rd wrote:
On Sunday, August 30, 2020 at 9:11:07 AM UTC-7,
jla...@highlandsniptechnology.com wrote:

I start an LC oscillator when I get a trigger, and use it to time
out
delays. The ADC is clocked from an OCXO and observes the
waveform of
the triggered LC oscillator, and I close a loop to lock the LC to
the
XO. Actually, the LC frequency is whatever it wants to be. The math
gets ugly.

I\'m thinking along those same lines. If I can (quickly!) measure the
phase angle between my XO and my triggered oscillator, I can seize the
initial phase offset and close a loop on that. ...

My triggered LC oscillator is great for a couple of microseconds, but
is piling up drift and jitter. It needs to be locked to a good XO
long-term.

This makes no sense; if you lock it to the XO with any variant of
phase-locking,
it\'s NO LONGER phase-locked to the trigger event, and the measurement
is worthless.
Just cancel the trigger-caused start phase against an XO-caused start
phase,
and ignore the absolute frequency of the LC entirely (unless you think
it drifts
enough in a few milliseconds to matter).


You\'ve never actually used a state-of-the-art digital delay generator, I
gather. Good ones have jitter down around 10 ps over fairly long
periods. Even the SRS DG535 I bought ~25 years ago had jitter less than
100 ps, and newer ones are much better.

The idea that an LC oscillator could hold the necessary phase accuracy
for milliseconds is ridiculous.



The od HP5359a time synthesiser  of similar vintage, should do that as
well...

Seems like it was 100 ps typical vs ~10 ps guaranteed for a modern one,
and only over a much shorter delay.

Making a really good DDG is a hard problem, for sure. I\'ve never built
one myself, but I\'ve happily used several, mostly SRS.

In my current incarnation I have a Highland P400, which is my go-to
pulse generator for most quickish things. Right now I\'m working on a
POC for a bathymetric lidar, which will use the P400 and some coax
cables to clock a dozen or so fast T/Hs at different delays.

Good medicine.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Phil Hobbs]

On 2020-08-30 19:41, jlarkin@highlandsniptechnology.com wrote:

On Sun, 30 Aug 2020 19:28:23 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-08-30 19:17, Chris wrote:
On 08/28/20 17:47, Phil Hobbs wrote:
On 2020-08-26 14:47, Chris wrote:
On 08/26/20 19:40, piglet wrote:
On 26/08/2020 5:58 pm, Gerhard Hoffmann wrote:
Am 26.08.20 um 18:29 schrieb Chris:


The older high end HP spectrum analysers, the 8566 and 8568 did that
as well.  The marketing blurb called it lock and roll, locking the
LO at start of sweep, then free running it open loop for the rest
of the sweep. Allowed them to have a stable 10Hz resolution bw and
1KHz span at Ghz, in the late 1970\'s.

I think what I was really saying was, was if the solution gets too
complex, it maybe the wrong approach ...

IIRC, there was an article in the HP Journal about this.
I think I have it on paper somewhere, but HP Journal
is probably searchable somewhere.

Cheers, Gerhard

This one?
http://hparchive.com/Journals/HPJ-1978-06.pdf

piglet


I think i\'ve seen that.Amazing bit of kit for it\'s time. HP really
were at the peak of their game back then with tech prowess few,
if any could match. Much of it still in use today.

Last catalog price for the 8566, iirc, was 78,000 usd and yet,
they sold bucketloads of them...

Back in 1982, when I was working in satcom, we had a reasonably new
Ailtech 757 (iirc). It was a manually-tuned gizmo that drifted around a
bit before it warmed up.

Then we got a swoopy new HP 8566A, later upgraded to a B. I was hooked.
I had one for awhile at IBM, and about 6 years I bought a used one on
eBay when I needed more top end than my previous 8568B. Its close-in
phase noise is remarkably low on account of its YIG-tuned sweep
oscillator.

Its main drawback is that you can have the RF or microwave band
displayed, but not both at once. Still, for 2 cents on the dollar one
really can\'t complain too loudly.

Cheers

Phil Hobbs


Most of the older HP analysers drifted a lot and needed a warmup period
of anything up to an hour before they were fit to use. Both the 8566 and
8568 were a step function improvement, in that they were ready for use
almost right away, Both use the same display section and the 10Hz
resolution bw option is makes them great for close in pjhase noise
checking.

Have one of each here, came from an rf / emc lab amd must have been on
24/7. Both display sections had a fuzzy tube, but got on to the John
Miles site and restored them back to sharp focus. Don\'t know how long
they will last, but only used occasionally, so not a problem. Still a
lot of them in use apparently, probably because they have a spec that\'s
difficult to match even now...

Chris


And getting harder. The SDR-based analyzers are so cheap that they\'re
taking over the market.

Cheers

Phil \"YIG-tuned forever\" Hobbs

Isn\'t a YIG frequency determined by the mag field? How can that be
controlled to PPB precision?

It has a super-high Q and a narrow control bandwidth. SDRs have all
sorts of sample clock jitter that a DBM driven from a YIG-tuned
oscillator avoids. The difference is 30-50 dB close-in phase noise,
nothing subtle at all, at all.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[whit3rd]

On Sunday, August 30, 2020 at 4:06:50 PM UTC-7, Phil Hobbs wrote:

On 2020-08-30 17:08, whit3rd wrote:

... if you lock it to the XO with any variant of phase-locking,
it\'s NO LONGER phase-locked to the trigger event, and the measurement is worthless.
Just cancel the trigger-caused start phase against an XO-caused start phase,
and ignore the absolute frequency of the LC entirely (unless you think it drifts
enough in a few milliseconds to matter).

You\'ve never actually used a state-of-the-art digital delay generator, I
gather. Good ones have jitter down around 10 ps over fairly long
periods. Even the SRS DG535 I bought ~25 years ago had jitter less than
100 ps, and newer ones are much better.

The idea that an LC oscillator could hold the necessary phase accuracy
for milliseconds is ridiculous.

There\'s no milliseconds required on phase accuracy; that\'s only for the LC
frequency drift from a measurement cycle to a subsequent calibration cycle. It\'s not necessary
for the LC to give an accurate sine, just a repeatable waveform, and any jitter is
irrelevant except as an addition to the thermal-noise contribution.

 

[Bill Sloman]

On Monday, August 31, 2020 at 1:59:13 AM UTC+10, Phil Hobbs wrote:

On 2020-08-26 11:00, jla...@highlandsniptechnology.com wrote:
On Wed, 26 Aug 2020 14:44:47 +0100, Chris <xxx.sys...@gfsys.co.uk
wrote:

On 08/26/20 03:24, jla...@highlandsniptechnology.com wrote:
On Tue, 25 Aug 2020 18:42:22 -0700 (PDT), \"John Miles, KE5FX\"
jmi...@gmail.com> wrote:

On Tuesday, August 25, 2020 at 11:34:31 AM UTC-7, John Larkin wrote:

<snip>

Just rereading this thread. How about sampling the XO when the trigger
appears, at the same time starting the LC. If you know which half-cycle
the XO is on (which isn\'t too hard to do) you can compute the I/Q
coefficients that make the initial phases of the LC and XO match. (For
extra credit, two XOs locked in quadrature would allow you to always be
on a good part of the slope, as well as disambiguating the quadrants.)

Just start a ramp and stop it on the next clock edge - actually the next clock edge but one to make sure that the ramp has been ramping long enough that initial transients have gone away, then digitise where the ramp has got to.

Digitising a sine wave and the complementary cosine wave would have worked just as well.

Two ADCs would have been more expensive than our ramp generating circuit (which was just a couple of 5GHz broad-band transistors) but it is certainly a more elegant solution.

The cosine wave wouldn\'t have to be exactly complementary if you kept track of the actual phase difference from the notionally in-quadrature waveforms (which wouldn\'t be difficult).

The start a ramp and stop it approach what we did back in 1988. There was a lot of auto-calibration - which got repeated every few minutes - to make sure that the ramp voltage we digitised started at the bottom of the range of the ADC we were using and always stopped just before the top of the range.

We used slow DACs to set the starting point of the ramp and and the current charging the capaictor.

Having pairs of delay board with a built-in delay generator made this pretty straight-forward (compared with some of the other stuff we were doing).

I spent a lot of time talking to the guys who wrote the software that made the system work, but I didn\'t have to discuss that bit - it all worked. I\'m sure that there were holes in my original specification, but the guy that implemented the system was really good (and found that aspect of the design tricky enough to be interesting), and the guy who took over after he went away was pretty good and very thorough (and - very nominally - my boss from then to the end of the project).

--
Bill Sloman, Sydney

 

[Phil Hobbs]

On 2020-08-30 20:58, whit3rd wrote:

On Sunday, August 30, 2020 at 4:06:50 PM UTC-7, Phil Hobbs wrote:
On 2020-08-30 17:08, whit3rd wrote:

... if you lock it to the XO with any variant of phase-locking,
it\'s NO LONGER phase-locked to the trigger event, and the
measurement is worthless. Just cancel the trigger-caused start
phase against an XO-caused start phase, and ignore the absolute
frequency of the LC entirely (unless you think it drifts enough
in a few milliseconds to matter).


You\'ve never actually used a state-of-the-art digital delay
generator, I gather. Good ones have jitter down around 10 ps over
fairly long periods. Even the SRS DG535 I bought ~25 years ago had
jitter less than 100 ps, and newer ones are much better.

The idea that an LC oscillator could hold the necessary phase
accuracy for milliseconds is ridiculous.

There\'s no milliseconds required on phase accuracy;

As the wise man said, \"When you find yourself in a hole, stop digging.\"

Reiterating point 1: you\'ve obviously never used a state-of-the-art DDG,
at least not at a level where you needed to knew what it did.

that\'s only for the LC frequency drift from a measurement cycle to a
subsequent calibration cycle. It\'s not necessary for the LC to give
an accurate sine, just a repeatable waveform, and any jitter is
irrelevant

An accurate, repeatable, low-jitter delay on an asynchronous waveform is
what a DDG is all about. See point 1.

> except as an addition to the thermal-noise contribution.

How would you estimate the thermal noise contribution exactly?

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[whit3rd]

On Sunday, August 30, 2020 at 6:48:58 PM UTC-7, Phil Hobbs wrote:

On 2020-08-30 20:58, whit3rd wrote:
On Sunday, August 30, 2020 at 4:06:50 PM UTC-7, Phil Hobbs wrote:
On 2020-08-30 17:08, whit3rd wrote:

... if you lock it to the XO with any variant of phase-locking,
it\'s NO LONGER phase-locked to the trigger event, and the
measurement is worthless. Just cancel the trigger-caused start
phase against an XO-caused start phase, and ignore the absolute
frequency of the LC entirely (unless you think it drifts enough
in a few milliseconds to matter).


You\'ve never actually used a state-of-the-art digital delay
generator, I gather. Good ones have jitter down around 10 ps over
fairly long periods. Even the SRS DG535 I bought ~25 years ago had
jitter less than 100 ps, and newer ones are much better.

The idea that an LC oscillator could hold the necessary phase
accuracy for milliseconds is ridiculous.

There\'s no milliseconds required on phase accuracy;

As the wise man said, \"When you find yourself in a hole, stop digging.\"

Reiterating point 1: you\'ve obviously never used a state-of-the-art DDG,
at least not at a level where you needed to knew what it did.

But this is about a triggered LC generator, not about a delay.
Why would a digital delay generator be involved?

that\'s only for the LC frequency drift from a measurement cycle to a
subsequent calibration cycle. It\'s not necessary for the LC to give
an accurate sine, just a repeatable waveform, and any jitter is
irrelevant

An accurate, repeatable, low-jitter delay on an asynchronous waveform is
what a DDG is all about. See point 1.

except as an addition to the thermal-noise contribution.

How would you estimate the thermal noise contribution exactly?

Minimize, not estimate; you have to buffer the LC waveform into an ADC,
and that means the buffer amp has some high input impedance, and presumably
introduces its own noise (or if you lower the input Z, pulls the LC amplitude or
frequency).

 

[server]

On Sun, 30 Aug 2020 21:48:49 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-08-30 20:58, whit3rd wrote:
On Sunday, August 30, 2020 at 4:06:50 PM UTC-7, Phil Hobbs wrote:
On 2020-08-30 17:08, whit3rd wrote:

... if you lock it to the XO with any variant of phase-locking,
it\'s NO LONGER phase-locked to the trigger event, and the
measurement is worthless. Just cancel the trigger-caused start
phase against an XO-caused start phase, and ignore the absolute
frequency of the LC entirely (unless you think it drifts enough
in a few milliseconds to matter).


You\'ve never actually used a state-of-the-art digital delay
generator, I gather. Good ones have jitter down around 10 ps over
fairly long periods. Even the SRS DG535 I bought ~25 years ago had
jitter less than 100 ps, and newer ones are much better.

The idea that an LC oscillator could hold the necessary phase
accuracy for milliseconds is ridiculous.

There\'s no milliseconds required on phase accuracy;

As the wise man said, \"When you find yourself in a hole, stop digging.\"

Reiterating point 1: you\'ve obviously never used a state-of-the-art DDG,
at least not at a level where you needed to knew what it did.

that\'s only for the LC frequency drift from a measurement cycle to a
subsequent calibration cycle. It\'s not necessary for the LC to give
an accurate sine, just a repeatable waveform, and any jitter is
irrelevant

An accurate, repeatable, low-jitter delay on an asynchronous waveform is
what a DDG is all about. See point 1.

except as an addition to the thermal-noise contribution.

How would you estimate the thermal noise contribution exactly?

Cheers

Phil Hobbs

A pretty good triggered LC oscillator will pile up jitter at very
roughly 1 picosecond RMS per microsecond. The junk it takes to start
and stop it compromise the Q some. So it\'s good to close the PLL and
lock it to a crystal within a microsecond or two.

A cheap XO will have jitter of maybe 20 ns RMS per second, less if you
get a good one by accident. A $70 OCXO will be roughly a thousand
times better.

The XO or OCXO will improve greatly with a cover to keep air currents
from wafting over it.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[John Miles, KE5FX]

On Friday, August 28, 2020 at 9:47:41 AM UTC-7, Phil Hobbs wrote:

Its main drawback is that you can have the RF or microwave band
displayed, but not both at once. Still, for 2 cents on the dollar one
really can\'t complain too loudly.

Sure it can!

http://www.ke5fx.com/sweep_0_24G.gif

In single-sweep mode at least...

-- john, KE5FX

 

[Jan Panteltje]

On a sunny day (Sun, 30 Aug 2020 14:08:38 -0700 (PDT)) it happened whit3rd
<whit3rd@gmail.com> wrote in
<fcef7b0c-f98d-4e4f-8577-91824ca64d2co@googlegroups.com>:

On Sunday, August 30, 2020 at 9:11:07 AM UTC-7, jla...@highlandsniptechnology.com wrote:

I start an LC oscillator when I get a trigger, and use it to time out
delays. The ADC is clocked from an OCXO and observes the waveform of
the triggered LC oscillator, and I close a loop to lock the LC to the
XO. Actually, the LC frequency is whatever it wants to be. The math
gets ugly.

I\'m thinking along those same lines. If I can (quickly!) measure the
phase angle between my XO and my triggered oscillator, I can seize the
initial phase offset and close a loop on that. ...

My triggered LC oscillator is great for a couple of microseconds, but
is piling up drift and jitter. It needs to be locked to a good XO
long-term.

This makes no sense; if you lock it to the XO with any variant of phase-locking,
it\'s NO LONGER phase-locked to the trigger event, and the measurement is worthless.
Just cancel the trigger-caused start phase against an XO-caused start phase,
and ignore the absolute frequency of the LC entirely (unless you think it drifts
enough in a few milliseconds to matter).

Indeed.
Perhaps if you PLL the LC to a precision reference and set its frequency via a DAC and varicap,
that would be like tuning a tuning fork by removing or adding some weight as in the mechanical equivalent,
and then leave it (maybe do that calibration just before the measurement, calibration button?,
Trigger would be like pinging a precisely tuned crystal / tuning fork.
The tuning needs not happen _during_ the trigger, assuming drift is OK?

Anyways he also writes mF (milli Farad) if he means uF (micro Farad) I think, so ..
factor a couple of thousand, so maybe it is not so critical ;-)

 

[Phil Hobbs]

On 2020-08-30 23:05, John Miles, KE5FX wrote:

On Friday, August 28, 2020 at 9:47:41 AM UTC-7, Phil Hobbs wrote:
Its main drawback is that you can have the RF or microwave band
displayed, but not both at once. Still, for 2 cents on the dollar one
really can\'t complain too loudly.

Sure it can!

http://www.ke5fx.com/sweep_0_24G.gif

In single-sweep mode at least...

I\'m a happy user of your GPIB Tools via a Prologix GPIB-Ethernet
adapter. Thanks for making them available!

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Phil Hobbs]

On 2020-08-30 22:46, jlarkin@highlandsniptechnology.com wrote:

On Sun, 30 Aug 2020 21:48:49 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-08-30 20:58, whit3rd wrote:
On Sunday, August 30, 2020 at 4:06:50 PM UTC-7, Phil Hobbs wrote:
On 2020-08-30 17:08, whit3rd wrote:

... if you lock it to the XO with any variant of phase-locking,
it\'s NO LONGER phase-locked to the trigger event, and the
measurement is worthless. Just cancel the trigger-caused start
phase against an XO-caused start phase, and ignore the absolute
frequency of the LC entirely (unless you think it drifts enough
in a few milliseconds to matter).


You\'ve never actually used a state-of-the-art digital delay
generator, I gather. Good ones have jitter down around 10 ps over
fairly long periods. Even the SRS DG535 I bought ~25 years ago had
jitter less than 100 ps, and newer ones are much better.

The idea that an LC oscillator could hold the necessary phase
accuracy for milliseconds is ridiculous.

There\'s no milliseconds required on phase accuracy;

As the wise man said, \"When you find yourself in a hole, stop digging.\"

Reiterating point 1: you\'ve obviously never used a state-of-the-art DDG,
at least not at a level where you needed to knew what it did.

that\'s only for the LC frequency drift from a measurement cycle to a
subsequent calibration cycle. It\'s not necessary for the LC to give
an accurate sine, just a repeatable waveform, and any jitter is
irrelevant

An accurate, repeatable, low-jitter delay on an asynchronous waveform is
what a DDG is all about. See point 1.

except as an addition to the thermal-noise contribution.

How would you estimate the thermal noise contribution exactly?

Cheers

Phil Hobbs

A pretty good triggered LC oscillator will pile up jitter at very
roughly 1 picosecond RMS per microsecond. The junk it takes to start
and stop it compromise the Q some. So it\'s good to close the PLL and
lock it to a crystal within a microsecond or two.

A cheap XO will have jitter of maybe 20 ns RMS per second, less if you
get a good one by accident. A $70 OCXO will be roughly a thousand
times better.

The XO or OCXO will improve greatly with a cover to keep air currents
from wafting over it.

Especially at low modulation frequencies. Gerhard and I were discussing
that yesterday in the tantalum caps thread--thermal drifts give rise to
very steeply rising baseband noise.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com