PLL tricks

On Sun, 21 Sep 2014 08:05:08 -0700 (PDT), Bill Sloman
<bill.sloman@gmail.com> wrote:

On Monday, 22 September 2014 00:41:15 UTC+10, k...@attt.bizz wrote:
On Sun, 21 Sep 2014 16:15:54 +1000, Bill Sloman <bill.sloman@ieee.org
wrote:
On 21/09/2014 3:04 PM, krw@attt.bizz wrote:
On Sat, 20 Sep 2014 21:53:06 -0700 (PDT), Bill Sloman
bill.sloman@gmail.com> wrote:
On Sunday, 21 September 2014 12:57:41 UTC+10, DecadentLinuxUserNumeroUno wrote:
On Sat, 20 Sep 2014 18:05:38 -0700 (PDT), Bill Sloman
bill.sloman@gmail.com> Gave us:

snip

More lies, but you're incapable of doing otherwise.

You may think so.

You keep reinforcing the proposition, with every post. Keep it up.

>It's not a particularly reliable opinion, since you seem to detect a lot more deliberate lies than anybody else, which does suggest that your truth/lies catagorisation scheme generates a lot more "lie" outputs than it should.

Not an opinion. You support it with every post.

snip

Dear me. Another krw look-alike.

More lies, but that's only to be expected of a liar.

"Liar" in krw-speak means anybody whose opinions krw doesn't share.

No, but you're simply proving my point. You're incapable of telling
the truth.

Or you are incapable of recognising it.

The real-world translation is "sane person".

You've never looked at one in the mirror, that's certain.

As "certain" as any other of krw's claims.

I only have what *you* say to go on. You lie, constantly. It must be
a compulsion.

One doesn't need to know much about the
USA to realise that the TEA Party are bunch of political lemmings trying
to make a society that is moving the wrong way - becoming even more inegalitarian - even more dysfunctional.

More lies but nothing new.

It certainly isn't a point of view that krw could be expected to share.

Facts are not a "point of view".

Krw again congratulates me on being saner than he is - not a
particularly ringing endorsement, since even Jamie qualifies for it.

Once again, you prove my point. You *are* incapable of telling the
truth.

Or you are incapable of recognising it, even when it is blatantly obvious to less demented observers.

I recognize you lies, well enough. It doesn't take much intelligence.
Even you *should* be able to see them.

 

On Sun, 21 Sep 2014 11:10:12 -0400, "Maynard A. Philbrook Jr."
<jamie_ka1lpa@charter.net> wrote:

In article <loot1a9ud84ef4h6jasi66ngiv337scr95@4ax.com>, krw@attt.bizz
says...
the truth.

The real-world translation is "sane person".

You've never looked at one in the mirror, that's certain.

One doesn't need to know much about the
USA to realise that the TEA Party are bunch of political lemmings trying
to make a society that is moving the wrong way - becoming even more inegalitarian - even more dysfunctional.

More lies but nothing new.

Krw again congratulates me on being saner than he is - not a
particularly ringing endorsement, since even Jamie qualifies for it.

Once again, you prove my point. You *are* incapable of telling the
truth.



In Bill's case, the truth has to be known before it can be told.

He's been told the truth often enough but keeps spouting the same
lies. That pushes it out of the ignorance realm.

> Evidents thus far, shows that may never happen.

 

On Sun, 21 Sep 2014 11:52:29 -0400, "Maynard A. Philbrook Jr."
<jamie_ka1lpa@charter.net> wrote:

In article <d981c10d-f1e2-4721-a489-8b3998c1371c@googlegroups.com>,
bill.sloman@gmail.com says...
Yes, you have endured your entire life being a good
little subservient follower, believing everything they
spoon fed you.

I'm sure that you and krw can believe this. My employers and colleagues always found me irritatingly sceptical, but then they were all a bit smarter than you are.

--
Bill Sloman, Sydney




You mean you had them fooled?

He was eventually found out. He hasn't been able to hold a job for
well over a decade. No one wants a liar around.

 

[DecadentLinuxUserNumeroUn]

On Sun, 21 Sep 2014 12:16:48 -0400, krw@attt.bizz Gave us:

On Sun, 21 Sep 2014 11:52:29 -0400, "Maynard A. Philbrook Jr."
jamie_ka1lpa@charter.net> wrote:

You mean you had them fooled?

He was eventually found out. He hasn't been able to hold a job for
well over a decade. No one wants a liar around.

I was thinking that has has been unemployable for over two decades.

But unlike the constantly lying Sloman idiot, I *will* delare what I
just stated as being only a guess.

 

[Tom Swift]

dagmargoodboat@yahoo.com wrote:

On Saturday, September 20, 2014 11:58:16 PM UTC-4, Tom Swift wrote:

Your return email address bounced so here's my reply:

Odd. Your first e-mail came through fine, yet Mr. Heath's went to the
spam box. Yahoo, ironically, is getting uppity.

It was probably the DMARC header in the replyto. I forgot to delete it. My
email host screws it up and the emails get bounced. Here's some information
in case you find it happens often:

"http://en.wikipedia.org/wiki/Domain-based_Message_Authentication,
_Reporting_%26_Conformance"

Some more:

"http://dmarc.org/overview.html"

The cure is to simply delete the replyto line in the header. This forces
the email client to use the From: address which probably doesn't have the
DMARC info.

 

On Sunday, September 21, 2014 3:51:50 PM UTC-4, Kevin Aylward wrote:

On Saturday, September 20, 2014 4:09:04 AM UTC-4, Tom Swift wrote:
dagmargoo...@yahoo.com wrote:

I scanned Matthys' articles to .PDF, if anyone wants them.
[1] Crystal Oscillator Circuits for VHF, Robert Matthys, RF Design,
May/June 1983 p62
[2] A High-Performance VHF Crystal Oscillator
Circuit, Robert Matthys, RF Design, March 1987, p31-38

I would like copies. Can you upload them to some file host?

E-mail is all I've got, but I'd be happy to send them your way.

Mail me at my posted address (it's good), and I'll send you the
articles.

Thanks for the files James.

Sure thing Kevin.

Similar descriptions to the several er..." legacy" oscillator books I have
at work. What I will say is that, by and large, pretty much ALL these
techniques have been superseded in commercial mass market precision
oscillators from oscillator vendors. These, ahmmm... legacy methods try and
achieve several competing performance criteria, e.g, noise, frequency verses
power supply voltage, temp stability etc by a using a few parts. As a
result, they never compete with todays methods.

Modern oscillator asics typically use one transistor for the oscillator, and
5000 more to do all the analog bits, that get you real performance. For
example, my asics have several independent LDOs. The LDO for the oscillator
has a nominal 100dB PSRR. So what would have been a few ppm per volt for a
raw xtal oscillator variation, is headed to < ppb.

Luxury!

Temperature stability is
dealt with by multi order chebychev polynomial correction. Variactors are
linearized by non-linear processing etc... All this for a 20 cent bit of
silicon. The oscillator itself is designed only for lowest phase noise.

Yep.

This ovenized VCXO specs -188dBc/Hz @ 100KHz, and -108dBc/Hz @ 10Hz offset:
http://www.wenzel.com/wp-content/parts/501-25900.pdf

Using digital tempco correction would save a lot of power.

All
other defects corrected by throwing transistors at it.

That makes sense. I was quite interested in doing the same nearly 20 years
ago, adding a uC to a VCXO for all those benefits. That's why I collected
a lot of oscillator / crystal literature.

I realized I'd be in the oscillator-making business then though, which wasn't
what I really wanted to do the rest of my life.

Small world, isn't it?

Cheers,
James Arthur

 

On Sunday, September 21, 2014 6:27:44 PM UTC-4, Clifford Heath wrote:

On 20/09/14 14:58, dagmargoo...@yahoo.com wrote:

I scanned Matthys' articles to .PDF, if anyone wants them.

[1] Crystal Oscillator Circuits for VHF, Robert Matthys, RF Designm May/June 1983 p62

[2] A High-Performance VHF Crystal Oscillator Circuit, Robert Matthys, RF Design, March 1987, p31-38

With Dagmar's approval, I've put those two files on my Dropbox. get them
here:

https://www.dropbox.com/sh/qjxmn9p836mwvw5/AAAqB1YSil4ZGL9ZS3a_q35Qa?dl=0

Thanks Dagmar!

Thanks Clifford, very considerate of you. I'm sure many people will
appreciate it.

Cheers,
James Arthur

 

[Bill Sloman]

On Monday, 22 September 2014 01:55:39 UTC+10, Maynard A. Philbrook Jr. wrote:

In article <8568b3e1-3f41-4c42-a30c-b80f3358d2a0@googlegroups.com>,
bill.sloman@gmail.com says...

In Bill's case, the truth has to be known before it can be told.

In krw's case, the "truth" was made known to krw by a process of divine revelation. Krw was a bit too dim to notice that creature doing the revelating had horns and a forked tail.

Evidents thus far, shows that may never happen.

Jamie probably meant "evidence" but since he doesn't understand the concept of evidence, it's not surprising that he hasn't master the spelling of the word either.

It really doesn't matter, the facts have been laid out

Where?

and you have been exposed.

It's as simple as that. What's left is protecting others from you.

You seem to have as ignorant of what constitutes "evidence" and "proof" as krw. But the image of you protecting the rest of the use group from my misinformation is thoroughly comical.

For once you made an amusing and entertaining observation.

--
Bill Sloman, Sydney

 

[Bill Sloman]

On Monday, 22 September 2014 02:13:08 UTC+10, k...@attt.bizz wrote:

On Sun, 21 Sep 2014 08:05:08 -0700 (PDT), Bill Sloman
bill.sloman@gmail.com> wrote:
On Monday, 22 September 2014 00:41:15 UTC+10, k...@attt.bizz wrote:
On Sun, 21 Sep 2014 16:15:54 +1000, Bill Sloman <bill.sloman@ieee.org
wrote:
On 21/09/2014 3:04 PM, krw@attt.bizz wrote:
On Sat, 20 Sep 2014 21:53:06 -0700 (PDT), Bill Sloman
bill.sloman@gmail.com> wrote:
On Sunday, 21 September 2014 12:57:41 UTC+10, DecadentLinuxUserNumeroUno wrote:
On Sat, 20 Sep 2014 18:05:38 -0700 (PDT), Bill Sloman
bill.sloman@gmail.com> Gave us:

<snip>

> Facts are not a "point of view".

Perhaps. But all your "facts" are merely your own assertions. You don't back them up with links to more objective observers, so what you parade as "facts" (and you don't much of that) are all observed from your peculiar point of view.

Krw again congratulates me on being saner than he is - not a
particularly ringing endorsement, since even Jamie qualifies for it.

Once again, you prove my point.

If you had any grasp of what constitutes argument or proof, you might be able to support that claim - though if you did you'd probably realise that you couldn't support it.

--
Bill Sloman, Sydney

 

[Bill Sloman]

On Monday, 22 September 2014 02:16:48 UTC+10, k...@attt.bizz wrote:

On Sun, 21 Sep 2014 11:52:29 -0400, "Maynard A. Philbrook Jr."
jamie_ka1lpa@charter.net> wrote:
In article <d981c10d-f1e2-4721-a489-8b3998c1371c@googlegroups.com>,
bill.sloman@gmail.com says...

<snip>

He was eventually found out. He hasn't been able to hold a job for
well over a decade. No one wants a liar around.

I haven't been able to get a job for over a decade - since I turned 61. I lost the last job I had - at Haffmans BV, Venlo in the Netherlands - because of Dutch red tape, not through any moral turpitude.

Krw has been told this often enough, but because he can't absorb information that doesn't conform to his prejudices, he keeps on making misleading claims.

--
Bill Sloman, Sydney

 

[Bill Sloman]

On Monday, 22 September 2014 02:23:46 UTC+10, DecadentLinuxUserNumeroUno wrote:

On Sun, 21 Sep 2014 12:16:48 -0400, krw@attt.bizz Gave us:
On Sun, 21 Sep 2014 11:52:29 -0400, "Maynard A. Philbrook Jr."
jamie_ka1lpa@charter.net> wrote:

You mean you had them fooled?

He was eventually found out. He hasn't been able to hold a job for
well over a decade. No one wants a liar around.

The last job I had was with Haffmans BV, Venlo, and they let me go at
the end of May 2003. If they'd kept me on any longer, the job would
have become permanent, rather than temporary (under Dutch employment
law), and I'd have automatically become a member of the pension fund
- with the immediate right to take early retirement. The pension fund
wanted a company contribution equal to 67% of my salary to cover that
risk, which would have made me very expensive.

> I was thinking that has has been unemployable for over two decades.

Something of an exaggeration. The fact that I'd got the job at Haffmans
at age 57 was a minor miracle, and reflected the fact that I was
decidedly employable, if - by Dutch standards - unattractively elderly.

But unlike the constantly lying Sloman idiot, I *will* delare what I
just stated as being only a guess.

Which gives you a rather higher moral status than krw.

--
Bill Sloman, Sydney

 

[Bill Sloman]

On Monday, 22 September 2014 02:34:58 UTC+10, dagmarg...@yahoo.com wrote:

On Sunday, September 21, 2014 10:52:25 AM UTC-4, Bill Sloman wrote:
On Monday, 22 September 2014 00:33:58 UTC+10, dagmarg...@yahoo.com wrote:
On Saturday, September 20, 2014 11:58:16 PM UTC-4, Tom Swift wrote:
dagmargoo...@yahoo.com wrote:

snip

Unfortunately that article only scans legibly in gray-scale, which makes the file size impractical.

Can you run it through character-recognition software?

The software that came with my cheap Epson printer/scanner - a Stylus NX635 - seems to do that automatically when I ask for a .pdf output, and it does seem to generate reasonably compact files.

I might try another computer. The one I scanned it on has excellent OCR
text accuracy, but strips *all* the formatting and puts the text in odd
places.

I've got a few more choices on the office computer.

I seem to remember that your attitude to office computers was nearly as Spartan as your attitude to central heating. Something modern and fast might do better.

--
Bill Sloman, Sydney

 

[Kevin Aylward]

wrote in message
news:c9a916d5-a530-445f-a742-6173417cef09@googlegroups.com...

On Saturday, September 20, 2014 4:09:04 AM UTC-4, Tom Swift wrote:

dagmargoodboat@yahoo.com wrote:

I scanned Matthys' articles to .PDF, if anyone wants them.
[1] Crystal Oscillator Circuits for VHF, Robert Matthys, RF Design,
May/June 1983 p62
[2] A High-Performance VHF Crystal Oscillator
Circuit, Robert Matthys, RF Design, March 1987, p31-38

I would like copies. Can you upload them to some file host?

E-mail is all I've got, but I'd be happy to send them your way.

Mail me at my posted address (it's good), and I'll send you the
articles.

Thanks for the files James.

Similar descriptions to the several er..." legacy" oscillator books I have
at work. What I will say is that, by and large, pretty much ALL these
techniques have been superseded in commercial mass market precision
oscillators from oscillator vendors. These, ahmmm... legacy methods try and
achieve several competing performance criteria, e.g, noise, frequency verses
power supply voltage, temp stability etc by a using a few parts. As a
result, they never compete with todays methods.

Modern oscillator asics typically use one transistor for the oscillator, and
5000 more to do all the analog bits, that get you real performance. For
example, my asics have several independent LDOs. The LDO for the oscillator
has a nominal 100dB PSRR. So what would have been a few ppm per volt for a
raw xtal oscillator variation, is headed to < ppb. Temperature stability is
dealt with by multi order chebychev polynomial correction. Variactors are
linearized by non-linear processing etc... All this for a 20 cent bit of
silicon. The oscillator itself is designed only for lowest phase noise. All
other defects corrected by throwing transistors at it.


Kevin Aylward
www.kevinaylward.co.uk
www.anasoft.co.uk - SuperSpice

 

[rickman]

On 9/21/2014 11:02 AM, John Larkin wrote:

On 20 Sep 2014 01:34:45 GMT, Jasen Betts <jasen@xnet.co.nz> wrote:

On 2014-09-19, John Larkin <jlarkin@highlandtechnology.com> wrote:
On Fri, 19 Sep 2014 15:32:07 -0500, ChesterW <iamsnoozin@yahoo.com
wrote:

Anyway, I make your 155.52 MHz oscillator with 0.2 ps rms jitter as
containing 15.0 bits of information. When it degrades to 12.7 bits
you're on the edge of your 1 ps error budget. That and how fast it
degrades should set the performance requirements on the feedback loop.

ChesterW


Seems to me that more modulation of a sine wave carries more
information, not less.

Does a perfect sine wave convey an infinite amount of information?

yes, frequency, amplitude, and phase to infinite precision.

The information is:

F = 1

A = 1

P = 0

How is that an infinite amount of information? It doesn't look very
interesting to me. Sime waves are boring anyhow.

You mean F = 1.0000000.... etc.

Yeah, they are boring if you look at them as discreet like digital.

--

Rick

 

[ChesterW]

On 9/19/14, 7:37 PM, John Larkin wrote:

On Fri, 19 Sep 2014 18:15:11 -0500, ChesterW <iamsnoozin@yahoo.com
wrote:

On 9/19/14, 4:21 PM, John Larkin wrote:
On Fri, 19 Sep 2014 15:32:07 -0500, ChesterW <iamsnoozin@yahoo.com
wrote:

On 9/16/14, 10:27 AM, John Larkin wrote:
On Tue, 16 Sep 2014 00:21:44 -0500, ChesterW <iamsnoozin@yahoo.com
wrote:

On 9/15/14, 4:55 PM, Phil Hobbs wrote:
snip



*----------------<----------------------------------------*
| |
VCXO *-----* *-----* *-------* |
155.52 MHz ->-- /1944 ->-|D Q|------|D Q|---| LOOP |----*
| | | | | |FILTER |
V *--^--* *--^--* *-------*
| | |
*------->-------* *---<----10MHz REF
Resynch B-B phase det

With maybe a second DFF stage between the phase detector and the loop
filter, to get rid of any noise caused by metastability.

Cheers

Phil Hobbs

It's elegant, but it seems counter-intuitive that the rather tough specs
can be met when throwing away over 99% of the phase comparison
information (1-1/125).

ChesterW

For a constant loop bandwidth, you should get some noise averaging by
doing the phase comparison faster, I agree. However, since you have to
crank down the BW to filter out the gross amounts of ripple from a
bang-bang phase detector, I expect that it won't be that different
inside the BW.

Of course, losing all that loop bandwidth does mean that the VCXO has to
be a lot better than it would with a 10 MHz comparison frequency.

Using local feedback, i.e. a DDS-based or fractional-N loop (wide loop
BW but probably fairly horrible drift) inside an 80-kHz bang-bang loop
would relax the requirements on the VCXO proper.

This is all such fun that I may have to try building something like that.

Cheers

Phil Hobbs


Yes, John Larkin gets the prize for the most interesting project of the
week. Lucky dog.

Here's a possible idea for evaluating the feasibility of different
schemes. Calculate the entropy of the 155.52 MHz signal. Estimate the
frequency drift of the VCXO and represent it as the number of bits of
information lost per 12.5 us update period. Then the feedback needs to
supply at least this number of bits of information to be a possible
solution. If the required feedback SNR is too high, then you know you
need to use the information from more phase comparisons, not just the
easy 12.5 us ones.


Something like that. We'll probably lay out a nice multilayer proto
board with a few candidate VCXO locations, 10 MHz filters, and
dipswitches and trimpots in the loop lowpass filter to make it easy to
tune. Seed that with SMA connectors for analysis, and experiment. Good
intern sort of project.

Putting a cover over the XO, to keep air currents off it, can reduce
jitter a lot.


This is cool:

https://dl.dropboxusercontent.com/u/53724080/Software/PhaseNoise.exe

It was done by one of the s.e.d. guys some time ago; Jeroen? It lets
you convert a phase noise curve to RMS jitter.


Whatever gets results is good. I wonder how intern errors sum. I don't
think it's a half power law, although I suppose it depends on the
intern. Maybe you can hire the re-incarnation of Claude Shannon.

I'm biased toward lots calculation and simulation before building and
fiddling - for complicated systems anyhow. I think it's from working
early in my career without much theory. That was frustrating as hell.

Anyway, I make your 155.52 MHz oscillator with 0.2 ps rms jitter as
containing 15.0 bits of information. When it degrades to 12.7 bits
you're on the edge of your 1 ps error budget. That and how fast it
degrades should set the performance requirements on the feedback loop.

ChesterW


Seems to me that more modulation of a sine wave carries more
information, not less.

Does a perfect sine wave convey an infinite amount of information?



The answer depends on un-supplied details.

In the sense of sending data using a carrier, then more modulation can
mean more information content. It depends on the determinism of the
modulation.

In the sense of sending data using a carrier, then a perfect sine wave
with infinite extent in time conveys zero information.

In the sense of a time reference, a perfect sine wave with zero error
conveys infinite information.

So how about that, the same signal conveys both zero and infinite
information, depending on the question. Reminds me of a story about
imaginary cows that I may post later.

In your oscillator problem I modeled the system as a clock with each
reference tick happening at 1/155.52 MHz. The 0.2 ps rms jitter is the
uncertainty in the time measurement. For these numbers, that's about 1
part in 32k, which requires about 15.0 bits to specify. Since the jitter
is random from cycle to cycle, this represents the maximum precision of
the system which I take as the information content of the (perfectly
aligned) system related to timing.

When the error from sources besides jitter accumulates to your spec of 1
ps, then the system is precise to about 1 part in 6400, or about 12.7
bits. So, when random occurrences cause your system to drift from
perfectly aligned to just out of spec, the time reference has lost about
2.3 bits of information.

So, if you know the drift rate of the timing of the system, then you can
calculate the data loss rate in bits per second. Since bits per second,
bandwidth, and SNR are related in the channel capacity formula, this may
be a tool to evaluate feedback schemes. If the feedback can't supply
enough bps, then it can't control the loop. I think this might set a
necessary but not sufficient condition, which at least may keep you from
wasting time building something that has no chance of working, which of
course is the purpose of analysis in engineering.

ChesterW


Just because you can divide two things that are in the same units, and
convert the result to bits, doesn't mean you should!

The test for the feedback system I gave before should be an easy bar to
pass. I think that because approaching the Shannon limit typically
requires significant cleverness on the part of the designer, and the
limits placed on the feedback loop by your requirement for speed and
precision probably limit the feedback system to fairly simple modulation
methods. These simple methods will likely fall well short of the maximum
theoretical limit on information transfer given by the channel capacity
formula.

A test that calculates the information content of a specific feedback
signal should come a lot closer to a necessary and sufficient condition.

Calculating and measuring information is just another tool. Eschewing it
is a bit like never learning about Fourier transforms or relying on
intuition instead of Boolean algebra when designing combinatorial logic.
One can get along without these things, they just need to be
significantly smarter than if they had used the available tools. I think
that once a certain level of education and experience is reached that
the major limits are in intuition and imagination. I know I can
certainly use all of the helpful tools I can get.

Anyone who thinks information theory is only of academic interest and is
of no use to 'real' designers should read about the work of Claude
Berrou and the founding of Qualcomm.

This has been fun, but I have to get back to work now. Deadlines loom.

ChesterW

 

[John Larkin]

On Sun, 21 Sep 2014 16:57:51 -0500, ChesterW <iamsnoozin@yahoo.com>
wrote:

On 9/19/14, 7:37 PM, John Larkin wrote:
On Fri, 19 Sep 2014 18:15:11 -0500, ChesterW <iamsnoozin@yahoo.com
wrote:

On 9/19/14, 4:21 PM, John Larkin wrote:
On Fri, 19 Sep 2014 15:32:07 -0500, ChesterW <iamsnoozin@yahoo.com
wrote:

On 9/16/14, 10:27 AM, John Larkin wrote:
On Tue, 16 Sep 2014 00:21:44 -0500, ChesterW <iamsnoozin@yahoo.com
wrote:

On 9/15/14, 4:55 PM, Phil Hobbs wrote:
snip



*----------------<----------------------------------------*
| |
VCXO *-----* *-----* *-------* |
155.52 MHz ->-- /1944 ->-|D Q|------|D Q|---| LOOP |----*
| | | | | |FILTER |
V *--^--* *--^--* *-------*
| | |
*------->-------* *---<----10MHz REF
Resynch B-B phase det

With maybe a second DFF stage between the phase detector and the loop
filter, to get rid of any noise caused by metastability.

Cheers

Phil Hobbs

It's elegant, but it seems counter-intuitive that the rather tough specs
can be met when throwing away over 99% of the phase comparison
information (1-1/125).

ChesterW

For a constant loop bandwidth, you should get some noise averaging by
doing the phase comparison faster, I agree. However, since you have to
crank down the BW to filter out the gross amounts of ripple from a
bang-bang phase detector, I expect that it won't be that different
inside the BW.

Of course, losing all that loop bandwidth does mean that the VCXO has to
be a lot better than it would with a 10 MHz comparison frequency.

Using local feedback, i.e. a DDS-based or fractional-N loop (wide loop
BW but probably fairly horrible drift) inside an 80-kHz bang-bang loop
would relax the requirements on the VCXO proper.

This is all such fun that I may have to try building something like that.

Cheers

Phil Hobbs


Yes, John Larkin gets the prize for the most interesting project of the
week. Lucky dog.

Here's a possible idea for evaluating the feasibility of different
schemes. Calculate the entropy of the 155.52 MHz signal. Estimate the
frequency drift of the VCXO and represent it as the number of bits of
information lost per 12.5 us update period. Then the feedback needs to
supply at least this number of bits of information to be a possible
solution. If the required feedback SNR is too high, then you know you
need to use the information from more phase comparisons, not just the
easy 12.5 us ones.


Something like that. We'll probably lay out a nice multilayer proto
board with a few candidate VCXO locations, 10 MHz filters, and
dipswitches and trimpots in the loop lowpass filter to make it easy to
tune. Seed that with SMA connectors for analysis, and experiment. Good
intern sort of project.

Putting a cover over the XO, to keep air currents off it, can reduce
jitter a lot.


This is cool:

https://dl.dropboxusercontent.com/u/53724080/Software/PhaseNoise.exe

It was done by one of the s.e.d. guys some time ago; Jeroen? It lets
you convert a phase noise curve to RMS jitter.


Whatever gets results is good. I wonder how intern errors sum. I don't
think it's a half power law, although I suppose it depends on the
intern. Maybe you can hire the re-incarnation of Claude Shannon.

I'm biased toward lots calculation and simulation before building and
fiddling - for complicated systems anyhow. I think it's from working
early in my career without much theory. That was frustrating as hell.

Anyway, I make your 155.52 MHz oscillator with 0.2 ps rms jitter as
containing 15.0 bits of information. When it degrades to 12.7 bits
you're on the edge of your 1 ps error budget. That and how fast it
degrades should set the performance requirements on the feedback loop.

ChesterW


Seems to me that more modulation of a sine wave carries more
information, not less.

Does a perfect sine wave convey an infinite amount of information?



The answer depends on un-supplied details.

In the sense of sending data using a carrier, then more modulation can
mean more information content. It depends on the determinism of the
modulation.

In the sense of sending data using a carrier, then a perfect sine wave
with infinite extent in time conveys zero information.

In the sense of a time reference, a perfect sine wave with zero error
conveys infinite information.

So how about that, the same signal conveys both zero and infinite
information, depending on the question. Reminds me of a story about
imaginary cows that I may post later.

In your oscillator problem I modeled the system as a clock with each
reference tick happening at 1/155.52 MHz. The 0.2 ps rms jitter is the
uncertainty in the time measurement. For these numbers, that's about 1
part in 32k, which requires about 15.0 bits to specify. Since the jitter
is random from cycle to cycle, this represents the maximum precision of
the system which I take as the information content of the (perfectly
aligned) system related to timing.

When the error from sources besides jitter accumulates to your spec of 1
ps, then the system is precise to about 1 part in 6400, or about 12.7
bits. So, when random occurrences cause your system to drift from
perfectly aligned to just out of spec, the time reference has lost about
2.3 bits of information.

So, if you know the drift rate of the timing of the system, then you can
calculate the data loss rate in bits per second. Since bits per second,
bandwidth, and SNR are related in the channel capacity formula, this may
be a tool to evaluate feedback schemes. If the feedback can't supply
enough bps, then it can't control the loop. I think this might set a
necessary but not sufficient condition, which at least may keep you from
wasting time building something that has no chance of working, which of
course is the purpose of analysis in engineering.

ChesterW


Just because you can divide two things that are in the same units, and
convert the result to bits, doesn't mean you should!



The test for the feedback system I gave before should be an easy bar to
pass. I think that because approaching the Shannon limit typically
requires significant cleverness on the part of the designer, and the
limits placed on the feedback loop by your requirement for speed and
precision probably limit the feedback system to fairly simple modulation
methods. These simple methods will likely fall well short of the maximum
theoretical limit on information transfer given by the channel capacity
formula.

What channel do you refer to?

A test that calculates the information content of a specific feedback
signal should come a lot closer to a necessary and sufficient condition.

Calculating and measuring information is just another tool. Eschewing it
is a bit like never learning about Fourier transforms or relying on
intuition instead of Boolean algebra when designing combinatorial logic.

Funny, but I never use Boolean logic or Karnaugh maps or any of those
classic things. I just look at things and draw logic. Given that FPGAs
are LUT based, and compilers do logic reduction for you (whether you
want them to or not), that old stuff hardly matters any more.

One can get along without these things, they just need to be
significantly smarter than if they had used the available tools. I think
that once a certain level of education and experience is reached that
the major limits are in intuition and imagination. I know I can
certainly use all of the helpful tools I can get.

Anyone who thinks information theory is only of academic interest and is
of no use to 'real' designers should read about the work of Claude
Berrou and the founding of Qualcomm.

I can't see how information theory is especially helpful in my PLL
problem. It's a control loop issue.


--

John Larkin Highland Technology, Inc

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Clifford Heath]

On 20/09/14 14:58, dagmargoodboat@yahoo.com wrote:

On Friday, September 19, 2014 2:44:55 PM UTC-4, Kevin Aylward wrote:
An inductor can be placed across the resistor to
reduce LF noise, but its limited in practice to avoid parasitic
oscillations.
At great personal peril, for the benefit of the group I descended into the
dungeon, fetched the Matthys articles, and fled.

Matthys and another guy, Belcher, report loaded, in-circuit Qs of 70K - 80K
for 5th-overtone 100MHz quartz crystal harmonic oscillators.

The technique is to run the rock series-resonant, and load it with a
common-base stage's emitter. Drive comes to the xtal's other terminal
from the collector via a simple network.

The effective resistance of the load being super-low, the ESR (namely,
the dissipative loss) added to the crystal is minimized, and Q maintained.

I scanned Matthys' articles to .PDF, if anyone wants them.
[1] Crystal Oscillator Circuits for VHF, Robert Matthys, RF Designm May/June 1983 p62
[2] A High-Performance VHF Crystal Oscillator Circuit, Robert Matthys, RF Design, March 1987, p31-38

With Dagmar's approval, I've put those two files on my Dropbox. get them
here:

<https://www.dropbox.com/sh/qjxmn9p836mwvw5/AAAqB1YSil4ZGL9ZS3a_q35Qa?dl=0>

Thanks Dagmar!

Clifford Heath.

 

On Saturday, September 20, 2014 5:58:00 AM UTC-4, Jan Panteltje wrote:

On a sunny day (Fri, 19 Sep 2014 21:58:16 -0700 (PDT)) it happened

dagmargoo...@yahoo.com wrote:

Here's a web-accessible example from Wenzel:
http://crovencrystals.com/applications/clockosc.htm

Nice.

Given VCOs with resonators of Q>=70K+, that translates to a crystal 3dB
passband on the order of 2-3KHz @ 155MHz. I'm not immediately sure if
that means 80KHz phase comparisons are enough to keep it on track, but
at least it doesn't look ridiculous...

I mentioned microwave bricks...KE5FX has a schematic for one here:
http://www.ke5fx.com/brick/fwbrick.pdf

Microwaves... If you want a free running oscillator,
then the litte ceramic pucks in the satellite LNBs are 9.something and 10.something GHz,
and have really really low noise.

I have a few of those--they're neat. I'm not sure what the resonator Q's
range is. I assumed for starters that making 10GHz to make 155.52 MHz
was getting there the hard way!

The little yellowish disks on the right:
http://panteltje.com/pub/5_dollar_LNB_PCB_IMG_3582.GIF

Yep, those are DROs (dielectric resonator oscillators), I think. The
structures at 10 and 8 o'clock look like tapped tuned feedback across
the c/e (or more likely s/d) of the transistor.

You can bring these down in frequency by mechanical loading, for example by gluing some
parts of a broken one on it.

So mechanical vibrations at 10 GHz, and cheap.

The key is finding a stable piezo or dielectric material with low
frictional or dielectric losses. Quartz wins for mechanical vibration.

One project on the table here is converting a standard LNB to a transmitter for the 10.5 GHz ham band, DVB-S.

This is done by changing the input and output of the 10 GHz pre-amp so it drives the horn,
and is fed from the (ring diode) mixer.

Very low power that is.

And all is very very low phase noise, even after mixing up with those pucks.

http://www.pi6atv.com/index.php?option=com_docman&task=docclick&Itemid=126&bid=299&limitstart=0&limit=10

From:

http://www.pi6atv.com/content/view/47/108/

Now try to simulate that.

I couldn't read the .PCX (pictures(?), but the station display was awfully
cool.

Cheers,
James Arthur (catching up with sed posts...)

 

On Saturday, September 20, 2014 5:58:00 AM UTC-4, Jan Panteltje wrote:

On a sunny day (Fri, 19 Sep 2014 21:58:16 -0700 (PDT)) it happened

dagmargoo...@yahoo.com wrote:

Here's a web-accessible example from Wenzel:

http://crovencrystals.com/applications/clockosc.htm

Nice.

Given VCOs with resonators of Q>=70K+, that translates to a crystal 3dB
passband on the order of 2-3KHz @ 155MHz. I'm not immediately sure if
that means 80KHz phase comparisons are enough to keep it on track, but
at least it doesn't look ridiculous...

I mentioned microwave bricks...KE5FX has a schematic for one here:

http://www.ke5fx.com/brick/fwbrick.pdf

Microwaves... If you want a free running oscillator,
then the litte ceramic pucks in the satellite LNBs are 9.something and 10.something GHz,
and have really really low noise.

The little yellowish disks on the right:

http://panteltje.com/pub/5_dollar_LNB_PCB_IMG_3582.GIF

Q's up to 15K @ 10GHz, 7K @ 1 GHz.

http://www.token.com.tw/pdf/dielectric/dielectric-resonator-te.pdf


There's always YIG...

Mechanical cavities are another possibility.

I got Q > 300 from a piece of copper refrigeration tubing resonator
inside a tin can (Clabber Girl baking powder--can is nicely tinned,
solders beautifully) for a cavity @ 908MHz, once upon a time in a pinch.
(We had to block out traffic @ ~880 MHz, IIRC)

It wasn't even hard--worked first try.

But somehow I don't think John wants to dig this hard for eight units.
He could just buy one of the finer VCXOs, diode-sample at 80KHz, LPF,
and he's done.

Cheers,
James

 

[Jasen Betts]

On 2014-09-21, John Larkin <jlarkin@highlandtechnology.com> wrote:

On 20 Sep 2014 01:34:45 GMT, Jasen Betts <jasen@xnet.co.nz> wrote:

On 2014-09-19, John Larkin <jlarkin@highlandtechnology.com> wrote:
On Fri, 19 Sep 2014 15:32:07 -0500, ChesterW <iamsnoozin@yahoo.com
wrote:

Anyway, I make your 155.52 MHz oscillator with 0.2 ps rms jitter as
containing 15.0 bits of information. When it degrades to 12.7 bits
you're on the edge of your 1 ps error budget. That and how fast it
degrades should set the performance requirements on the feedback loop.

ChesterW


Seems to me that more modulation of a sine wave carries more
information, not less.

Does a perfect sine wave convey an infinite amount of information?

yes, frequency, amplitude, and phase to infinite precision.

The information is:

F = 1

A = 1

P = 0

How is that an infinite amount of information? It doesn't look very
interesting to me. Sime waves are boring anyhow.

it is if you know it's not
F.0.9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999


--
umop apisdn


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