really slow PLL...

[Clifford Heath]

On 24/7/22 05:00, Joe Gwinn wrote:

I forgot to mention one thing, a way to speed initialization up:

The external 1PPS pulse-train is taken as gospel. If one counts local
40 MHz oscillator cycles between any adjacent pair of 1PPS events, one
will get a very accurate measurement of the local oscillator signal
frequency. Knowing that it is supposed to be 40 MHz, one can compute
how far off correct (as a ratio) that local oscillator is from truth.
This can be used to jump far closer starting frequency to correct
without waiting for convergence to get there.

This initial measurement stands alone, not refining a previous body of
measurement knowledge, so it\'s reasonable to set the gain high. Human
perception does this a lot. If you hear two sounds a certain interval
apart, your hearing is pre-primed to expect a third at exactly the same
interval. If the third comes slightly early or slightly late, slightly
quieter or slightly louder, we jump to conclusions very quickly about
what\'s happening. Very rapid model-forming, and adapting new sensations
to refine the model. Very necessary for a prey animal!

Is there a name for this idea in filter terminology?

Clifford Heath

 

[Joe Gwinn]

On Sun, 24 Jul 2022 08:40:28 +1000, Clifford Heath
<no_spam@please.net> wrote:

On 24/7/22 05:00, Joe Gwinn wrote:
I forgot to mention one thing, a way to speed initialization up:

The external 1PPS pulse-train is taken as gospel. If one counts local
40 MHz oscillator cycles between any adjacent pair of 1PPS events, one
will get a very accurate measurement of the local oscillator signal
frequency. Knowing that it is supposed to be 40 MHz, one can compute
how far off correct (as a ratio) that local oscillator is from truth.
This can be used to jump far closer starting frequency to correct
without waiting for convergence to get there.

This initial measurement stands alone, not refining a previous body of
measurement knowledge, so it\'s reasonable to set the gain high. Human
perception does this a lot. If you hear two sounds a certain interval
apart, your hearing is pre-primed to expect a third at exactly the same
interval. If the third comes slightly early or slightly late, slightly
quieter or slightly louder, we jump to conclusions very quickly about
what\'s happening. Very rapid model-forming, and adapting new sensations
to refine the model. Very necessary for a prey animal!

Is there a name for this idea in filter terminology?

There are two answers, depending on which field you mean, biology or
electronics.

In biology, it has been long known that the brain creates a model of
the world, and keys on deviations between prediction and actual. But
this isn\'t just for expected rhythm, it\'s far more general and
flexible than that.

With the speedup algorithm I mentioned earlier, the mechanism is
designed with considerable domain knowledge in hand. The primary
driver is to achieve robustness despite the imperfections of real
clocks et al. The continuous look-ahead algorithm is not flummoxed by
non-stationary and/or non-Gaussian probability-distributions, et al.
But it\'s more in the nature of a control system than a filter per se.

Joe Gwinn

 

[Clifford Heath]

On 24/7/22 09:08, Joe Gwinn wrote:

On Sun, 24 Jul 2022 08:40:28 +1000, Clifford Heath
no_spam@please.net> wrote:

On 24/7/22 05:00, Joe Gwinn wrote:
I forgot to mention one thing, a way to speed initialization up:

The external 1PPS pulse-train is taken as gospel. If one counts local
40 MHz oscillator cycles between any adjacent pair of 1PPS events, one
will get a very accurate measurement of the local oscillator signal
frequency. Knowing that it is supposed to be 40 MHz, one can compute
how far off correct (as a ratio) that local oscillator is from truth.
This can be used to jump far closer starting frequency to correct
without waiting for convergence to get there.

This initial measurement stands alone, not refining a previous body of
measurement knowledge, so it\'s reasonable to set the gain high. Human
perception does this a lot. If you hear two sounds a certain interval
apart, your hearing is pre-primed to expect a third at exactly the same
interval. If the third comes slightly early or slightly late, slightly
quieter or slightly louder, we jump to conclusions very quickly about
what\'s happening. Very rapid model-forming, and adapting new sensations
to refine the model. Very necessary for a prey animal!

Is there a name for this idea in filter terminology?

There are two answers, depending on which field you mean, biology or
electronics.

In biology, it has been long known that the brain creates a model of
the world, and keys on deviations between prediction and actual. But
this isn\'t just for expected rhythm, it\'s far more general and
flexible than that.

With the speedup algorithm I mentioned earlier, the mechanism is
designed with considerable domain knowledge in hand. The primary
driver is to achieve robustness despite the imperfections of real
clocks et al. The continuous look-ahead algorithm is not flummoxed by
non-stationary and/or non-Gaussian probability-distributions, et al.

> But it\'s more in the nature of a control system than a filter per se.

A control system also models the plant, measures deviations from the
prediction, before it applies a loop filter to decide the corrective step.

That\'s the filter I\'m referring to. It\'s just the same pronciple with
the human system as when synchronising two clocks.

Clifford Heath

 

[Jan Panteltje]

On a sunny day (Sun, 24 Jul 2022 08:40:28 +1000) it happened Clifford Heath
<no_spam@please.net> wrote in
<1704967e2e98d7c6$38$2251891$26dd2c6e@news.thecubenet.com>:

On 24/7/22 05:00, Joe Gwinn wrote:
I forgot to mention one thing, a way to speed initialization up:

The external 1PPS pulse-train is taken as gospel. If one counts local
40 MHz oscillator cycles between any adjacent pair of 1PPS events, one
will get a very accurate measurement of the local oscillator signal
frequency. Knowing that it is supposed to be 40 MHz, one can compute
how far off correct (as a ratio) that local oscillator is from truth.
This can be used to jump far closer starting frequency to correct
without waiting for convergence to get there.

This initial measurement stands alone, not refining a previous body of
measurement knowledge, so it\'s reasonable to set the gain high. Human
perception does this a lot. If you hear two sounds a certain interval
apart, your hearing is pre-primed to expect a third at exactly the same
interval. If the third comes slightly early or slightly late, slightly
quieter or slightly louder, we jump to conclusions very quickly about
what\'s happening. Very rapid model-forming, and adapting new sensations
to refine the model. Very necessary for a prey animal!

Is there a name for this idea in filter terminology?

No sure, but this is related to \'the alien problem\' from cryptography.
It goes like:
Alien comes to earh, wants to take all knowledge humans have back home.
So he gets Encyclopedia Britannica, but it is too heavy and does not fit in his flying saucer.
So he writes the text out as an ASCII hex number and does 1 / that number.
then he takes a stick and puts a mark on it in that ratio
and takes the stick back home.

To say 3 ticks is all you need to convey all information in the universe
given time has no granularity.
The stick in that example does of course have, limited by size of atoms etc,
But does time have granularity?

I use this all the time.

 

[Joe Gwinn]

On Sun, 24 Jul 2022 08:58:10 GMT, Jan Panteltje
<pNaonStpealmtje@yahoo.com> wrote:

On a sunny day (Sun, 24 Jul 2022 08:40:28 +1000) it happened Clifford Heath
no_spam@please.net> wrote in
1704967e2e98d7c6$38$2251891$26dd2c6e@news.thecubenet.com>:

On 24/7/22 05:00, Joe Gwinn wrote:
I forgot to mention one thing, a way to speed initialization up:

The external 1PPS pulse-train is taken as gospel. If one counts local
40 MHz oscillator cycles between any adjacent pair of 1PPS events, one
will get a very accurate measurement of the local oscillator signal
frequency. Knowing that it is supposed to be 40 MHz, one can compute
how far off correct (as a ratio) that local oscillator is from truth.
This can be used to jump far closer starting frequency to correct
without waiting for convergence to get there.

This initial measurement stands alone, not refining a previous body of
measurement knowledge, so it\'s reasonable to set the gain high. Human
perception does this a lot. If you hear two sounds a certain interval
apart, your hearing is pre-primed to expect a third at exactly the same
interval. If the third comes slightly early or slightly late, slightly
quieter or slightly louder, we jump to conclusions very quickly about
what\'s happening. Very rapid model-forming, and adapting new sensations
to refine the model. Very necessary for a prey animal!

Is there a name for this idea in filter terminology?

No sure, but this is related to \'the alien problem\' from cryptography.
It goes like:
Alien comes to earh, wants to take all knowledge humans have back home.
So he gets Encyclopedia Britannica, but it is too heavy and does not fit in his flying saucer.
So he writes the text out as an ASCII hex number and does 1 / that number.
then he takes a stick and puts a mark on it in that ratio
and takes the stick back home.

To say 3 ticks is all you need to convey all information in the universe
given time has no granularity.
The stick in that example does of course have, limited by size of atoms etc,
But does time have granularity?

I use this all the time.

Time is thought to have a granularity of sorts, about 10^-43 seconds,
which is a Planck Unit.

..<https://en.wikipedia.org/wiki/Planck_units>

Joe Gwinn

 

[Joe Gwinn]

On Sun, 24 Jul 2022 16:46:15 +1000, Clifford Heath
<no_spam@please.net> wrote:

On 24/7/22 09:08, Joe Gwinn wrote:
On Sun, 24 Jul 2022 08:40:28 +1000, Clifford Heath
no_spam@please.net> wrote:

On 24/7/22 05:00, Joe Gwinn wrote:
I forgot to mention one thing, a way to speed initialization up:

The external 1PPS pulse-train is taken as gospel. If one counts local
40 MHz oscillator cycles between any adjacent pair of 1PPS events, one
will get a very accurate measurement of the local oscillator signal
frequency. Knowing that it is supposed to be 40 MHz, one can compute
how far off correct (as a ratio) that local oscillator is from truth.
This can be used to jump far closer starting frequency to correct
without waiting for convergence to get there.

This initial measurement stands alone, not refining a previous body of
measurement knowledge, so it\'s reasonable to set the gain high. Human
perception does this a lot. If you hear two sounds a certain interval
apart, your hearing is pre-primed to expect a third at exactly the same
interval. If the third comes slightly early or slightly late, slightly
quieter or slightly louder, we jump to conclusions very quickly about
what\'s happening. Very rapid model-forming, and adapting new sensations
to refine the model. Very necessary for a prey animal!

Is there a name for this idea in filter terminology?

There are two answers, depending on which field you mean, biology or
electronics.

In biology, it has been long known that the brain creates a model of
the world, and keys on deviations between prediction and actual. But
this isn\'t just for expected rhythm, it\'s far more general and
flexible than that.

With the speedup algorithm I mentioned earlier, the mechanism is
designed with considerable domain knowledge in hand. The primary
driver is to achieve robustness despite the imperfections of real
clocks et al. The continuous look-ahead algorithm is not flummoxed by
non-stationary and/or non-Gaussian probability-distributions, et al.


But it\'s more in the nature of a control system than a filter per se.

A control system also models the plant, measures deviations from the
prediction, before it applies a loop filter to decide the corrective step.

That\'s the filter I\'m referring to. It\'s just the same principle with
the human system as when synchronising two clocks.

Well, yes, but we\'re being a bit pedantic here. The problem is that
the word \"filter\" can have multiple meanings. Like the low-pass loop
filter in a PLL or FLL. In the algorithm described earlier, the FLL
loop filter is implicit in the choice of look-ahead and cycle times.

Joe Gwinn

Joe Gwinn

 

[Jan Panteltje]

On a sunny day (Sun, 24 Jul 2022 12:09:21 -0400) it happened Joe Gwinn
<joegwinn@comcast.net> wrote in <ugrqdhp9ldssd95u39nik1n6th9bktbs41@4ax.com>:

On Sun, 24 Jul 2022 08:58:10 GMT, Jan Panteltje
pNaonStpealmtje@yahoo.com> wrote:

On a sunny day (Sun, 24 Jul 2022 08:40:28 +1000) it happened Clifford Heath
no_spam@please.net> wrote in
1704967e2e98d7c6$38$2251891$26dd2c6e@news.thecubenet.com>:

On 24/7/22 05:00, Joe Gwinn wrote:
I forgot to mention one thing, a way to speed initialization up:

The external 1PPS pulse-train is taken as gospel. If one counts local
40 MHz oscillator cycles between any adjacent pair of 1PPS events, one
will get a very accurate measurement of the local oscillator signal
frequency. Knowing that it is supposed to be 40 MHz, one can compute
how far off correct (as a ratio) that local oscillator is from truth.
This can be used to jump far closer starting frequency to correct
without waiting for convergence to get there.

This initial measurement stands alone, not refining a previous body of
measurement knowledge, so it\'s reasonable to set the gain high. Human
perception does this a lot. If you hear two sounds a certain interval
apart, your hearing is pre-primed to expect a third at exactly the same
interval. If the third comes slightly early or slightly late, slightly
quieter or slightly louder, we jump to conclusions very quickly about
what\'s happening. Very rapid model-forming, and adapting new sensations
to refine the model. Very necessary for a prey animal!

Is there a name for this idea in filter terminology?

No sure, but this is related to \'the alien problem\' from cryptography.
It goes like:
Alien comes to earh, wants to take all knowledge humans have back home.
So he gets Encyclopedia Britannica, but it is too heavy and does not fit in his flying saucer.
So he writes the text out as an ASCII hex number and does 1 / that number.
then he takes a stick and puts a mark on it in that ratio
and takes the stick back home.

To say 3 ticks is all you need to convey all information in the universe
given time has no granularity.
The stick in that example does of course have, limited by size of atoms etc,
But does time have granularity?

I use this all the time.

Time is thought to have a granularity of sorts, about 10^-43 seconds,
which is a Planck Unit.

.<https://en.wikipedia.org/wiki/Planck_units

Sure but there is a problem, if you scroll down on that site you find the sentence
\"the Planck time is the time required for light to travel the distance of 1 Planck length in a vacuum\".
That leads to a circular reasoning, as traveling half a Planck length would take half the time...
Just before that the text goes into Planck length, and says in some theories with more dimensions
that length is smaller than the fundamental Planck length
So much twenty-first century physics assumptions...
Start of big bang start of time, obvious bull.
Maybe there are a zillion bangs like there are a zillion stars and something that formed those over time.
Measurement limits like saying length in feet or whatever ...
But sure, what we can measure, being made of matter, probably has a limit.
Wait till they figure out gravity.. I still like Le Sage\'s model as it provides a MECHANISM for gravity.
Now they are stuck looking for dark matter..

Very interesting, physics, BTW.

 

[Joe Gwinn]

On Sun, 24 Jul 2022 16:53:04 GMT, Jan Panteltje
<pNaonStpealmtje@yahoo.com> wrote:

On a sunny day (Sun, 24 Jul 2022 12:09:21 -0400) it happened Joe Gwinn
joegwinn@comcast.net> wrote in <ugrqdhp9ldssd95u39nik1n6th9bktbs41@4ax.com>:

On Sun, 24 Jul 2022 08:58:10 GMT, Jan Panteltje
pNaonStpealmtje@yahoo.com> wrote:

On a sunny day (Sun, 24 Jul 2022 08:40:28 +1000) it happened Clifford Heath
no_spam@please.net> wrote in
1704967e2e98d7c6$38$2251891$26dd2c6e@news.thecubenet.com>:

On 24/7/22 05:00, Joe Gwinn wrote:
I forgot to mention one thing, a way to speed initialization up:

The external 1PPS pulse-train is taken as gospel. If one counts local
40 MHz oscillator cycles between any adjacent pair of 1PPS events, one
will get a very accurate measurement of the local oscillator signal
frequency. Knowing that it is supposed to be 40 MHz, one can compute
how far off correct (as a ratio) that local oscillator is from truth.
This can be used to jump far closer starting frequency to correct
without waiting for convergence to get there.

This initial measurement stands alone, not refining a previous body of
measurement knowledge, so it\'s reasonable to set the gain high. Human
perception does this a lot. If you hear two sounds a certain interval
apart, your hearing is pre-primed to expect a third at exactly the same
interval. If the third comes slightly early or slightly late, slightly
quieter or slightly louder, we jump to conclusions very quickly about
what\'s happening. Very rapid model-forming, and adapting new sensations
to refine the model. Very necessary for a prey animal!

Is there a name for this idea in filter terminology?

No sure, but this is related to \'the alien problem\' from cryptography.
It goes like:
Alien comes to earh, wants to take all knowledge humans have back home.
So he gets Encyclopedia Britannica, but it is too heavy and does not fit in his flying saucer.
So he writes the text out as an ASCII hex number and does 1 / that number.
then he takes a stick and puts a mark on it in that ratio
and takes the stick back home.

To say 3 ticks is all you need to convey all information in the universe
given time has no granularity.
The stick in that example does of course have, limited by size of atoms etc,
But does time have granularity?

I use this all the time.

Time is thought to have a granularity of sorts, about 10^-43 seconds,
which is a Planck Unit.

.<https://en.wikipedia.org/wiki/Planck_units

Sure but there is a problem, if you scroll down on that site you find the sentence
\"the Planck time is the time required for light to travel the distance of 1 Planck length in a vacuum\".
That leads to a circular reasoning, as traveling half a Planck length would take half the time...
Just before that the text goes into Planck length, and says in some theories with more dimensions
that length is smaller than the fundamental Planck length

Well, with Planck Units, all these things are true at the same time,
and nobody knows if one causes another, or if all flow from a
currently unknown common cause. Or something.

I don\'t think that one can in fact move by less than a Planck length,
so in that case it is unclear if the limit is on time or on distance,
both, or something unobvious.

So much twenty-first century physics assumptions...
Start of big bang start of time, obvious bull.
Maybe there are a zillion bangs like there are a zillion stars and something that formed those over time.
Measurement limits like saying length in feet or whatever ...
But sure, what we can measure, being made of matter, probably has a limit.
Wait till they figure out gravity.. I still like Le Sage\'s model as it provides a MECHANISM for gravity.
Now they are stuck looking for dark matter..

All that mess is the best humans have come up with so far. Stay
tuned.

Very interesting, physics, BTW.

Not to mention weird.


Joe Gwinn

 

[server]

On Wed, 20 Jul 2022 16:20:57 -0700, John Larkin
<jlarkin@highland_atwork_technology.com> wrote:

Suppose I have several rackmount boxes and each has a BNC connector on
the back. Each of them has an open-drain mosfet, a weak pullup, and a
lowpass filtered schmitt gate back into our FPGA.

I can daisy-chain several boxes with BNC cables and tees.

Each box has a 40 MHz VCXO and I want to phase-lock them, or at least
time-align them to always be the same within a few microseconds,
longterm.

I could call one the leader (not \"master\") and make the others
followers (not \"slaves\") and have the leader make an active low pulse
maybe once a second. A follower would use her (not \"his\") clock to
measure the incoming period and tweak its local VCXO in the right
direction. That should work.

Don\'t GPS receivers lock their 10 MHz oscillators to a 1 PPS pulse
from the satellites?

My system should work from a 1 PPS GPS pulse too, all boxes as
followers.

The PLL algorithm might be interesting.

The ultimate way to do this would be to measure the phase of the xo at
every rise of the 1 pps input, to nanosecond or picosecond resolution.
That wouldn\'t be hard, but it would be overkill for the requirement to
time-align power supplies.

 

[Jasen Betts]

On 2022-07-20, John Larkin <jlarkin@highland_atwork_technology.com> wrote:

Suppose I have several rackmount boxes and each has a BNC connector on
the back. Each of them has an open-drain mosfet, a weak pullup, and a
lowpass filtered schmitt gate back into our FPGA.

I can daisy-chain several boxes with BNC cables and tees.

Each box has a 40 MHz VCXO and I want to phase-lock them, or at least
time-align them to always be the same within a few microseconds,
longterm.

If you only need a consensus, put the 40 mhz from the crystal onto the
BNC though some resistor, they\'ll sort it out, like a table full of metronoms.

If you have control loops all over the place pulling in different
directions maybe not so much.

I could call one the leader (not \"master\") and make the others
followers (not \"slaves\") and have the leader make an active low pulse
maybe once a second. A follower would use her (not \"his\") clock to
measure the incoming period and tweak its local VCXO in the right
direction. That should work.

Don\'t GPS receivers lock their 10 MHz oscillators to a 1 PPS pulse
from the satellites?

mostlky no.

--
Jasen.

 

[Joe Gwinn]

On Fri, 22 Jul 2022 09:03:16 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

Martin Brown wrote:
On 22/07/2022 03:44, Clifford Heath wrote:
On 22/7/22 03:10, Phil Hobbs wrote:
Gerhard Hoffmann wrote:
Am 21.07.22 um 16:15 schrieb Phil Hobbs:

I wonder if there\'s an advantage to using the closure phase for an
array that large.  With 17 oscillators you\'ve got 136 independent
phase differences, so maybe there\'s a way to get 22 dB instead of
12 dB improvement.

-v ?

what do you mean with closure phase? Where do the 22 dB come
from?

The idea was simply to have all 16 regulated to the be
synchronous and then feed them into a 16-to--1 Wilkinson
combiner. The phase noise should average out among the
16 units. Just as proof of concept. The MTI-260 are quite ok,
but with bleeding edge oscillators that could be interesting.
In the region where you just cannot improve an oscillator.

Cheers
Gerhard

Sure.  Thing is, that wastes a lot of information that you could
maybe use to get 10*log(136) = 21.3 dB improvement instead of
10*log(17) = 12.3 dB.  [136 = N(N-1)/2 when N = 17.]

Closure is a really cute idea, which I first came across in the
context of very long baseline interferometry (VLBI) radio telescopes.
See the discussion from BEOS 3e here:

https://electrooptical.net/www/sed/closure.png>.

Interesting, thanks.

Some frequency synthesiser chips employ proprietary majick to reduce
the phase noise associated with integer divide/multiply ratios.
Polyphase oscillator and slipping by partial cycles I think. Perhaps
they\'re doing something like closure against the different clock phases?

Quite probably - it has been known for a long time in radio astronomy
first derived by Jennison in 1958 at Jodrell Bank for 3 antennae. This
is the original ground breaking paper for anyone interested

https://articles.adsabs.harvard.edu//full/1958MNRAS.118..276J/0000276.000.html


(easier to understand versions exist today). WIki isn\'t bad:

https://en.wikipedia.org/wiki/Closure_phase

It allows you to get a good phase observable uncontaminated by the phase
error at each node for every distinct subset of 3 nodes. There is a
corresponding closure amplitude for distinct subsets of 4 nodes.

Obviously the bigger N is the more useful observables you can get which
is why the big dish telescopes sometimes stay on target and in the loop
for perhaps longer than they really ought to in deteriorating weather.

This book reviews most of the classical tricks used in VLBI and
interferometry from the period when they had just become routine:

Indirect Imaging: Measurement and Processing for Indirect Imaging
Editor-J. A. Roberts
 0 ratings by Goodreads
ISBN 10: 0521262828 / ISBN 13: 9780521262828
Published by Cambridge University Press, 1984

This proved hard to get:
..
<https://www.amazon.com/Indirect-Imaging-Measurement-Processing/dp/0521262828>

The real power comes from the number of independent observables from N
instruments going like N**2, so that you win SNR like N**2 instead of N.

Quite a startling improvement for moderate-to-large N!

All very interesting. I\'ve been digging, and came across a very
interesting article, which happens to be open-access, which is all too
uncommon.

\"A geometric view of closure phases in interferometry\", DOI:
<https://doi.org/10.1017/pasa.2022.6>

..<https://www.cambridge.org/core/journals/publications-of-the-astronomical-society-of-australia/article/geometric-view-of-closure-phases-in-interferometry/5E8A5A8D58A2FC72ADFA0587347C4DA7>


I\'m still digesting it, but basically deducing the underlying geometry
allowed for some significant improvements.

Joe Gwinn

 

[Gerhard Hoffmann]

Am 25.07.22 um 18:31 schrieb Joe Gwinn:

On Fri, 22 Jul 2022 09:03:16 -0400, Phil Hobbs

\"A geometric view of closure phases in interferometry\", DOI:
https://doi.org/10.1017/pasa.2022.6

.<https://www.cambridge.org/core/journals/publications-of-the-astronomical-society-of-australia/article/geometric-view-of-closure-phases-in-interferometry/5E8A5A8D58A2FC72ADFA0587347C4DA7


I\'m still digesting it, but basically deducing the underlying geometry
allowed for some significant improvements.

I have not yet digested it, but can I assume that it won\'t help
me to create a carrier that is phase noise wise better than
averaged over 16 oscillators created equally bad?

More suitable for post-processing after-the-fact?

U. Rohde has the math for n injection locked oscillators in one
of his books, but the formulas probably fall apart when you have
to insert hard numbers for real oscillators you can buy, or build.
Methinks he is more into multiple coupled resonators.

cheers,
Gerhard

 

[John Larkin]

On Fri, 22 Jul 2022 20:54:49 -0500, Les Cargill <lcargil99@gmail.com>
wrote:

Phil Hobbs wrote:
jlarkin@highlandsniptechnology.com wrote:
snip

It dithers around the setpoint but nobody notices.


That\'s what lowpass filters are for.

This is immune to classic control theory so the concept annoys some
people but it works great.

A real old time control guy like Tim Wescott would probably be a fan
too--the great virtue of a bang-bang controller is that (as you say)
it\'s highly resistant to variations in the _plant_.


Well, yeah - it\'s naturally constrained. When I jack the temp target on
the A/C here, it take 30-45 seconds to turn everything off.


Tim used to be a lot of fun and put up with much. FWIW rbj showed up
on Reddit and lasted a couple days.

Your furnace doesn\'t go nuts when you have a Christmas party, even
though all those people generate a lot of heat, and there\'s lots of
opening and closing of doors and ovens.


You\'re just doing trust falls with slew rate limiting. There\'s
probably a PhD paper somewhere with a madman low-pass filtering the
output of a bangbang with a lowpass.

We made a lot of timing modules for a big laser facility. We get a
155.52 MHz fiber data stream and lock a local VCO to that, with jitter
a couple of picoseconds. The phase detector, actually a time detector,
is an ECL d-flop in a bangbang loop.

The lowpass has switchable bandwidth, acquisition mode and track mode,
something like 8 KHz and 2 KHz.

 

[Joe Gwinn]

On Mon, 25 Jul 2022 20:51:18 +0200, Gerhard Hoffmann <dk4xp@arcor.de>
wrote:

Am 25.07.22 um 18:31 schrieb Joe Gwinn:
On Fri, 22 Jul 2022 09:03:16 -0400, Phil Hobbs

\"A geometric view of closure phases in interferometry\", DOI:
https://doi.org/10.1017/pasa.2022.6

.<https://www.cambridge.org/core/journals/publications-of-the-astronomical-society-of-australia/article/geometric-view-of-closure-phases-in-interferometry/5E8A5A8D58A2FC72ADFA0587347C4DA7


I\'m still digesting it, but basically deducing the underlying geometry
allowed for some significant improvements.

I have not yet digested it, but can I assume that it won\'t help
me to create a carrier that is phase noise wise better than
averaged over 16 oscillators created equally bad?

As you suspect, no, it won\'t. Only better oscillators will help.


>More suitable for post-processing after-the-fact?

The big advantage of closure-phase methods is that one can recover the
emission distribution of a very distant source by interferometry,
while ignoring various practical imperfections of radio/optical
telescope interferometers.

This works because the closure / kernel phase is an inherent property
of the source that is not affected by those practical imperfections.

This is how we image distant quasars and the event horizon of
billion-sun black holes at the center of some galaxies.

U. Rohde has the math for n injection locked oscillators in one
of his books, but the formulas probably fall apart when you have
to insert hard numbers for real oscillators you can buy, or build.
Methinks he is more into multiple coupled resonators.

Yes. The classic is a room full of pendulum clocks slipping into
synchrony. Discovered in 1666 by Christiaan Huygens, who invented of
the pendulum clock in 1657.

The only math needed is differential equations, developed a few years
later, in 1671. U. Rohde was a bit late to the party.


Joe Gwinn

 

[Gerhard Hoffmann]

Am 25.07.22 um 21:49 schrieb Joe Gwinn:

I have not yet digested it, but can I assume that it won\'t help
me to create a carrier that is phase noise wise better than
averaged over 16 oscillators created equally bad?

As you suspect, no, it won\'t. Only better oscillators will help.

Or even more oscillators to average.

Cheers, Gerhard

 

[Joe Gwinn]

On Mon, 25 Jul 2022 22:16:42 +0200, Gerhard Hoffmann <dk4xp@arcor.de>
wrote:

Am 25.07.22 um 21:49 schrieb Joe Gwinn:

I have not yet digested it, but can I assume that it won\'t help
me to create a carrier that is phase noise wise better than
averaged over 16 oscillators created equally bad?

As you suspect, no, it won\'t. Only better oscillators will help.

Or even more oscillators to average.

Yes, but the improvement is 5 dB per factor of ten oscillator count.
Longer integration times may be easier.

Low-noise oscillator design is a career.

Joe Gwinn

 

[Phil Hobbs]

Gerhard Hoffmann wrote:

Am 25.07.22 um 18:31 schrieb Joe Gwinn:
On Fri, 22 Jul 2022 09:03:16 -0400, Phil Hobbs

\"A geometric view of closure phases in interferometry\", DOI:
https://doi.org/10.1017/pasa.2022.6

.<https://www.cambridge.org/core/journals/publications-of-the-astronomical-society-of-australia/article/geometric-view-of-closure-phases-in-interferometry/5E8A5A8D58A2FC72ADFA0587347C4DA7



I\'m still digesting it, but basically deducing the underlying geometry
allowed for some significant improvements.

I have not yet digested it, but can I assume that it won\'t help
me to create a carrier that is phase noise wise better than
averaged over 16 oscillators created equally bad?

More suitable for post-processing after-the-fact?

U. Rohde has the math for n injection locked oscillators in one
of his books, but the formulas probably fall apart when you have
to insert hard numbers for real oscillators you can buy, or build.
Methinks he is more into multiple coupled resonators.

cheers,
Gerhard

I\'m not sure--as I say, I haven\'t got a properly-thought-out scheme, but
it seems as though it ought to be possible to combine the measurements
to produce N-1 oscillator signals, each one N times quieter, so that
averaging _those_ would get you to the N(N-1)/2 level.

It probably needs a whole lot of phase shifters or weighted summers
(like a Wilkinson with attenuators), so it may well not be a win from a
total-hardware POV. Seems like it would be worth a bit of thought, though.

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]

Joe Gwinn wrote:

On Mon, 25 Jul 2022 20:51:18 +0200, Gerhard Hoffmann <dk4xp@arcor.de
wrote:

Am 25.07.22 um 18:31 schrieb Joe Gwinn:
On Fri, 22 Jul 2022 09:03:16 -0400, Phil Hobbs

\"A geometric view of closure phases in interferometry\", DOI:
https://doi.org/10.1017/pasa.2022.6

.<https://www.cambridge.org/core/journals/publications-of-the-astronomical-society-of-australia/article/geometric-view-of-closure-phases-in-interferometry/5E8A5A8D58A2FC72ADFA0587347C4DA7


I\'m still digesting it, but basically deducing the underlying geometry
allowed for some significant improvements.

I have not yet digested it, but can I assume that it won\'t help
me to create a carrier that is phase noise wise better than
averaged over 16 oscillators created equally bad?

As you suspect, no, it won\'t. Only better oscillators will help.

As Kipling might say, \"Not so, but far otherwise.\"

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]

Joe Gwinn wrote:

On Mon, 25 Jul 2022 22:16:42 +0200, Gerhard Hoffmann <dk4xp@arcor.de
wrote:

Am 25.07.22 um 21:49 schrieb Joe Gwinn:

I have not yet digested it, but can I assume that it won\'t help
me to create a carrier that is phase noise wise better than
averaged over 16 oscillators created equally bad?

As you suspect, no, it won\'t. Only better oscillators will help.

Or even more oscillators to average.

Yes, but the improvement is 5 dB per factor of ten oscillator count.
Longer integration times may be easier.

Low-noise oscillator design is a career.

Joe Gwinn

Nah, even the simple averaging case you win SNR like N, so it\'s 10 dB
per decade.

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

 

[Gerhard Hoffmann]

Am 26.07.22 um 14:42 schrieb Phil Hobbs:

Joe Gwinn wrote:

Yes, but the improvement is 5 dB per factor of ten oscillator count.
Longer integration times may be easier.

Low-noise oscillator design is a career.

Joe Gwinn


Nah, even the simple averaging case you win SNR like N, so it\'s 10 dB
per decade.

3 dB per doubling the # of oscs.

So, it will probably be 2 groups of 8 for my cross-correlating Timepod .
As I wrote, the 5.0 MHz MTI-260 were relatively cheap.

> Cheers

Gerhard, DK4XP