1ns max jitter oscillator, cheap - for fast 4 diode sampler

[John Larkin]

On Thu, 9 May 2019 03:16:29 -0700 (PDT), klaus.kragelund@gmail.com
wrote:

On Thursday, 9 May 2019 04:54:34 UTC+2, John Larkin wrote:
On Wed, 8 May 2019 13:18:51 -0700 (PDT), klaus.kragelund@gmail.com
wrote:

On Tuesday, 7 May 2019 22:50:59 UTC+2, John Larkin wrote:
On Tue, 7 May 2019 12:42:22 -0700 (PDT), klaus.kragelund@gmail.com
wrote:

On Tuesday, 7 May 2019 17:18:48 UTC+2, John Larkin wrote:
On Tue, 7 May 2019 07:14:33 -0700 (PDT), klaus.kragelund@gmail.com
wrote:

Hi

I'm working on my ~3ns 4 diode sampler (preferable 1ns if possible)

So I need a pretty good oscillator, with low jitter

I have never needed a good oscillator before, so on this topic I am totally at square one

First I was thinking about an RC oscillator, and cleaning up the jitter. RC typically have 1us of jitter (found info on the web), and a crystal oscillator, standard type probably 1ns jitter. But I think that idea was crazy, a PLL clean up, would not work I guess.

In order to not mess up my measurement and keep the averaging low (I could do many samples and average), I would guess I need jitter of 300ps (10%) of my 3ns reolution)

But jitter is not listed as a search parameter. So where to start? (with low price in mind)

Cheers

Klaus

Do you want a continuous running oscillator, namely a crystal
oscillator? That works if the measured event and the sampler timebase
can run off the same clock. Even cheap XOs have picosecond or
sub-picosecond jitter measured over short time spans. Longer spans are
trashed by low frequency phase noise, numbers in the nanoseconds per
second for cheap XOs, picoseconds per second for good OCXOs.

That is a very good point, great catch.

I will be using it in a TDR, so short pulse, and build up waveform for reflected pulse. Since I need up to 200m lenth, the maximum time from the emitted pulse to reflected is 3us. So if the jitter is slowly changing over time, it may be a lot less in only that time span.


The simplest timebase is a linear RC ramp and a comparator and a DAC,
no clock at all. RMS jitter of 1 part in 20,000 isn't difficult,
1:50000 is challenging. So 3 us/20000 would be 150 ps RMS jitter,
which is probably OK. The echo from 200m of coax will be very soft,
and you can average to reduce displayed jitter. Cheat a little.

In this case I need a fast comparator, sub ns response time. They cost over 2 USD which is a lot more expensive than a picosecond timing PWM microcontroller

Cheers

Klaus

LVDS receivers make great fast RRIO comparators. We pay 55 cents for
SN65LVDS2DBVR.

Yes, that is cheap (a bit slower than my requirements)

But how do you use it as a comparator, since it has large tolerances on the receiver thresholds (100mV)?

Regards

Klaus

If you're doing a timing ramp, DC offset becomes time offset, and you
can cal that out. 1 ps RMS jitter and 1 ps delay resolution are
feasible with a reasonably fast ramp. The FIN1101, LVDS in and out, is
even better.

Somebody sells basically the same part, but they call it a comparator
and want $4 for it.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[DLUNU]

John Larkin <jjlarkin@highlandtechnology.com> wrote in
news:88j8dehdqrt0ok5ruo6l4k433bkbd7bpd4@4ax.com:

On Thu, 9 May 2019 10:30:11 -0400, bitrex <user@example.net> wrote:

On 5/9/19 9:33 AM, Phil Hobbs wrote:
On 5/7/19 4:57 PM, John Larkin wrote:
On Tue, 7 May 2019 15:39:04 -0400, bitrex <user@example.net
wrote:

On 5/7/19 3:08 PM, Tom Gardner wrote:
On 07/05/19 18:20, Cursitor Doom wrote:
On Tue, 07 May 2019 07:14:33 -0700, klaus.kragelund wrote:

Hi

I'm working on my ~3ns 4 diode sampler (preferable 1ns if
possible)

I know I'll appear a dinosaur by saying this, but you really
can't beat a
good old fashioned Wien Bridge oscillator when it comes to
spectral purity and low phase noise. They certainly beat the
crap out of any digital synthesis technique IMV.

No, but that statement is about as sensible as almost
all your statements.

He's right about the spectral purity and the phase noise can be
cleaned up by injection-locking it.

A sampler time base needs to stay phase coherent to a trigger.
Injection locking whacks randomly the phase. We care about time,
not frequency.

Sinusoidal injection locking of sinusoidal oscillators is a lot
gentler than square wave injection.

If oscillator 2 is phase-locked to oscillator 1 then ideally the
phase of oscillator 2 shouldn't be getting randomly "whacked" by
oscillator 1, yeah? they're locked - isn't that what "locking" is?
if oscillator 2's phase is getting randomly whacked then they
aren't locked!

If osc2 is started at some arbitrary trigger time and later locked
to crystal osc1, its phase will crawl to the phase of o1, which was
random relative to start time.

The trick is to lock it to the frequency of o1 but not drag its
phase around.

If you are happy with the phase of o1, why have o2?


It takes some time for a lock to occur though, like the two
metronomes on the board that can roll around on top of two tin
cans, so it's no good for instant on-off.

Right.


these?

MEMS oscillators are low jitter.


<https://www.digikey.com/en/product-highlight/s/sitime/low-jitter-
oscillators>

I wonder how noisey MEMES oscillators are...

 

[bitrex]

On 5/9/19 11:58 AM, John Larkin wrote:

On Thu, 9 May 2019 10:30:11 -0400, bitrex <user@example.net> wrote:

On 5/9/19 9:33 AM, Phil Hobbs wrote:
On 5/7/19 4:57 PM, John Larkin wrote:
On Tue, 7 May 2019 15:39:04 -0400, bitrex <user@example.net> wrote:

On 5/7/19 3:08 PM, Tom Gardner wrote:
On 07/05/19 18:20, Cursitor Doom wrote:
On Tue, 07 May 2019 07:14:33 -0700, klaus.kragelund wrote:

Hi

I'm working on my ~3ns 4 diode sampler (preferable 1ns if possible)

I know I'll appear a dinosaur by saying this, but you really can't
beat a
good old fashioned Wien Bridge oscillator when it comes to spectral
purity and low phase noise. They certainly beat the crap out of any
digital synthesis technique IMV.

No, but that statement is about as sensible as almost
all your statements.

He's right about the spectral purity and the phase noise can be cleaned
up by injection-locking it.

A sampler time base needs to stay phase coherent to a trigger.
Injection locking whacks randomly the phase. We care about time, not
frequency.

Sinusoidal injection locking of sinusoidal oscillators is a lot gentler
than square wave injection.

If oscillator 2 is phase-locked to oscillator 1 then ideally the phase
of oscillator 2 shouldn't be getting randomly "whacked" by oscillator 1,
yeah? they're locked - isn't that what "locking" is? if oscillator 2's
phase is getting randomly whacked then they aren't locked!

If osc2 is started at some arbitrary trigger time and later locked to
crystal osc1, its phase will crawl to the phase of o1, which was
random relative to start time.

The trick is to lock it to the frequency of o1 but not drag its phase
around.

If you are happy with the phase of o1, why have o2?

I guess the assumption we're working with here is that there are two
oscillators, one with low distortion/broadband noise but higher phase
noise, like a Wien bridge, and the other with better phase noise but
higher distortion/broadband noise like from a cheapo frequency
synthesizer. So through locking they ideally compensate for each other's
deficiencies.

At least that seems to be the thrust of the Analog Devices whitepaper on
the technique that GH posted. If you don't care about distortion or
broadband noise then I suppose it's irrelevant to have o2, but recall
that initially I was unsure of the purpose of the required oscillator I
thought it might be for testing the performance of the sampler/ADC
rather than clocking.

It takes some time for a lock to occur though, like the two metronomes
on the board that can roll around on top of two tin cans, so it's no
good for instant on-off.

Right.

 

[John Larkin]

On Thu, 9 May 2019 10:30:11 -0400, bitrex <user@example.net> wrote:

On 5/9/19 9:33 AM, Phil Hobbs wrote:
On 5/7/19 4:57 PM, John Larkin wrote:
On Tue, 7 May 2019 15:39:04 -0400, bitrex <user@example.net> wrote:

On 5/7/19 3:08 PM, Tom Gardner wrote:
On 07/05/19 18:20, Cursitor Doom wrote:
On Tue, 07 May 2019 07:14:33 -0700, klaus.kragelund wrote:

Hi

I'm working on my ~3ns 4 diode sampler (preferable 1ns if possible)

I know I'll appear a dinosaur by saying this, but you really can't
beat a
good old fashioned Wien Bridge oscillator when it comes to spectral
purity and low phase noise. They certainly beat the crap out of any
digital synthesis technique IMV.

No, but that statement is about as sensible as almost
all your statements.

He's right about the spectral purity and the phase noise can be cleaned
up by injection-locking it.

A sampler time base needs to stay phase coherent to a trigger.
Injection locking whacks randomly the phase. We care about time, not
frequency.

Sinusoidal injection locking of sinusoidal oscillators is a lot gentler
than square wave injection.

If oscillator 2 is phase-locked to oscillator 1 then ideally the phase
of oscillator 2 shouldn't be getting randomly "whacked" by oscillator 1,
yeah? they're locked - isn't that what "locking" is? if oscillator 2's
phase is getting randomly whacked then they aren't locked!

If osc2 is started at some arbitrary trigger time and later locked to
crystal osc1, its phase will crawl to the phase of o1, which was
random relative to start time.

The trick is to lock it to the frequency of o1 but not drag its phase
around.

If you are happy with the phase of o1, why have o2?

It takes some time for a lock to occur though, like the two metronomes
on the board that can roll around on top of two tin cans, so it's no
good for instant on-off.

Right.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

On Thursday, 9 May 2019 16:05:15 UTC+2, John Larkin wrote:

On Thu, 9 May 2019 03:16:29 -0700 (PDT), klaus.kragelund@gmail.com
wrote:

On Thursday, 9 May 2019 04:54:34 UTC+2, John Larkin wrote:
On Wed, 8 May 2019 13:18:51 -0700 (PDT), klaus.kragelund@gmail.com
wrote:

On Tuesday, 7 May 2019 22:50:59 UTC+2, John Larkin wrote:
On Tue, 7 May 2019 12:42:22 -0700 (PDT), klaus.kragelund@gmail.com
wrote:

On Tuesday, 7 May 2019 17:18:48 UTC+2, John Larkin wrote:
On Tue, 7 May 2019 07:14:33 -0700 (PDT), klaus.kragelund@gmail.com
wrote:

Hi

I'm working on my ~3ns 4 diode sampler (preferable 1ns if possible)

So I need a pretty good oscillator, with low jitter

I have never needed a good oscillator before, so on this topic I am totally at square one

First I was thinking about an RC oscillator, and cleaning up the jitter. RC typically have 1us of jitter (found info on the web), and a crystal oscillator, standard type probably 1ns jitter. But I think that idea was crazy, a PLL clean up, would not work I guess.

In order to not mess up my measurement and keep the averaging low (I could do many samples and average), I would guess I need jitter of 300ps (10%) of my 3ns reolution)

But jitter is not listed as a search parameter. So where to start? (with low price in mind)

Cheers

Klaus

Do you want a continuous running oscillator, namely a crystal
oscillator? That works if the measured event and the sampler timebase
can run off the same clock. Even cheap XOs have picosecond or
sub-picosecond jitter measured over short time spans. Longer spans are
trashed by low frequency phase noise, numbers in the nanoseconds per
second for cheap XOs, picoseconds per second for good OCXOs.

That is a very good point, great catch.

I will be using it in a TDR, so short pulse, and build up waveform for reflected pulse. Since I need up to 200m lenth, the maximum time from the emitted pulse to reflected is 3us. So if the jitter is slowly changing over time, it may be a lot less in only that time span.


The simplest timebase is a linear RC ramp and a comparator and a DAC,
no clock at all. RMS jitter of 1 part in 20,000 isn't difficult,
1:50000 is challenging. So 3 us/20000 would be 150 ps RMS jitter,
which is probably OK. The echo from 200m of coax will be very soft,
and you can average to reduce displayed jitter. Cheat a little.

In this case I need a fast comparator, sub ns response time. They cost over 2 USD which is a lot more expensive than a picosecond timing PWM microcontroller

Cheers

Klaus

LVDS receivers make great fast RRIO comparators. We pay 55 cents for
SN65LVDS2DBVR.

Yes, that is cheap (a bit slower than my requirements)

But how do you use it as a comparator, since it has large tolerances on the receiver thresholds (100mV)?

Regards

Klaus

If you're doing a timing ramp, DC offset becomes time offset, and you
can cal that out. 1 ps RMS jitter and 1 ps delay resolution are
feasible with a reasonably fast ramp. The FIN1101, LVDS in and out, is
even better.

Somebody sells basically the same part, but they call it a comparator
and want $4 for it.

You could probably do a slow calibration routine with the DAC with intervals, so thermal drifts effects are calibrated out

Cheers

Klaus

 

On Thursday, 9 May 2019 12:33:26 UTC+2, amal banerjee wrote:

On Tuesday, May 7, 2019 at 7:44:39 PM UTC+5:30, klaus.k...@gmail.com wrote:
Hi

I'm working on my ~3ns 4 diode sampler (preferable 1ns if possible)

So I need a pretty good oscillator, with low jitter

I have never needed a good oscillator before, so on this topic I am totally at square one

First I was thinking about an RC oscillator, and cleaning up the jitter.. RC typically have 1us of jitter (found info on the web), and a crystal oscillator, standard type probably 1ns jitter. But I think that idea was crazy, a PLL clean up, would not work I guess.

In order to not mess up my measurement and keep the averaging low (I could do many samples and average), I would guess I need jitter of 300ps (10%) of my 3ns reolution)

But jitter is not listed as a search parameter. So where to start? (with low price in mind)

Cheers

Klaus

Have you considered a common emitter negative resistance oscillator using some RF|microwave transistor - HFA3134, BFR92A etc?

Somewhere else in the thread, an LC oscillator was mentioned. I suggested maybe a Colpits. That is close to what you are suggesting, right?

Cheers

Klaus

 

[Clifford Heath]

On 10/5/19 5:21 am, klaus.kragelund@gmail.com wrote:

On Thursday, 9 May 2019 16:05:15 UTC+2, John Larkin wrote:
On Thu, 9 May 2019 03:16:29 -0700 (PDT), klaus.kragelund@gmail.com
wrote:

On Thursday, 9 May 2019 04:54:34 UTC+2, John Larkin wrote:
On Wed, 8 May 2019 13:18:51 -0700 (PDT), klaus.kragelund@gmail.com
wrote:

On Tuesday, 7 May 2019 22:50:59 UTC+2, John Larkin wrote:
On Tue, 7 May 2019 12:42:22 -0700 (PDT), klaus.kragelund@gmail.com
wrote:

On Tuesday, 7 May 2019 17:18:48 UTC+2, John Larkin wrote:
On Tue, 7 May 2019 07:14:33 -0700 (PDT), klaus.kragelund@gmail.com
wrote:

Hi

I'm working on my ~3ns 4 diode sampler (preferable 1ns if possible)

So I need a pretty good oscillator, with low jitter

I have never needed a good oscillator before, so on this topic I am totally at square one

First I was thinking about an RC oscillator, and cleaning up the jitter. RC typically have 1us of jitter (found info on the web), and a crystal oscillator, standard type probably 1ns jitter. But I think that idea was crazy, a PLL clean up, would not work I guess.

In order to not mess up my measurement and keep the averaging low (I could do many samples and average), I would guess I need jitter of 300ps (10%) of my 3ns reolution)

But jitter is not listed as a search parameter. So where to start? (with low price in mind)

Cheers

Klaus

Do you want a continuous running oscillator, namely a crystal
oscillator? That works if the measured event and the sampler timebase
can run off the same clock. Even cheap XOs have picosecond or
sub-picosecond jitter measured over short time spans. Longer spans are
trashed by low frequency phase noise, numbers in the nanoseconds per
second for cheap XOs, picoseconds per second for good OCXOs.

That is a very good point, great catch.

I will be using it in a TDR, so short pulse, and build up waveform for reflected pulse. Since I need up to 200m lenth, the maximum time from the emitted pulse to reflected is 3us. So if the jitter is slowly changing over time, it may be a lot less in only that time span.


The simplest timebase is a linear RC ramp and a comparator and a DAC,
no clock at all. RMS jitter of 1 part in 20,000 isn't difficult,
1:50000 is challenging. So 3 us/20000 would be 150 ps RMS jitter,
which is probably OK. The echo from 200m of coax will be very soft,
and you can average to reduce displayed jitter. Cheat a little.

In this case I need a fast comparator, sub ns response time. They cost over 2 USD which is a lot more expensive than a picosecond timing PWM microcontroller

Cheers

Klaus

LVDS receivers make great fast RRIO comparators. We pay 55 cents for
SN65LVDS2DBVR.

Yes, that is cheap (a bit slower than my requirements)

But how do you use it as a comparator, since it has large tolerances on the receiver thresholds (100mV)?

Regards

Klaus

If you're doing a timing ramp, DC offset becomes time offset, and you
can cal that out. 1 ps RMS jitter and 1 ps delay resolution are
feasible with a reasonably fast ramp. The FIN1101, LVDS in and out, is
even better.

Somebody sells basically the same part, but they call it a comparator
and want $4 for it.


You could probably do a slow calibration routine with the DAC with intervals, so thermal drifts effects are calibrated out

What sort of thermal drift in offset voltage does the SN65LVDS2DBVR
have? Perhaps that's a question for JL.

 

[Clifford Heath]

On 9/5/19 11:33 pm, Phil Hobbs wrote:

On 5/7/19 4:57 PM, John Larkin wrote:
On Tue, 7 May 2019 15:39:04 -0400, bitrex <user@example.net> wrote:

On 5/7/19 3:08 PM, Tom Gardner wrote:
On 07/05/19 18:20, Cursitor Doom wrote:
On Tue, 07 May 2019 07:14:33 -0700, klaus.kragelund wrote:

Hi

I'm working on my ~3ns 4 diode sampler (preferable 1ns if possible)

I know I'll appear a dinosaur by saying this, but you really can't
beat a
good old fashioned Wien Bridge oscillator when it comes to spectral
purity and low phase noise. They certainly beat the crap out of any
digital synthesis technique IMV.

No, but that statement is about as sensible as almost
all your statements.

He's right about the spectral purity and the phase noise can be cleaned
up by injection-locking it.

A sampler time base needs to stay phase coherent to a trigger.
Injection locking whacks randomly the phase. We care about time, not
frequency.

Sinusoidal injection locking of sinusoidal oscillators is a lot gentler
than square wave injection.

Or any injection that doesn't have much above F_0. The "whack" in square
wave injection comes from the series of odd harmonics, but the actual
locking is achieved by the F_0 component.

Clifford Heath.

 

[Phil Hobbs]

On 5/9/19 9:55 PM, Clifford Heath wrote:

On 9/5/19 11:33 pm, Phil Hobbs wrote:
On 5/7/19 4:57 PM, John Larkin wrote:
On Tue, 7 May 2019 15:39:04 -0400, bitrex <user@example.net> wrote:

On 5/7/19 3:08 PM, Tom Gardner wrote:
On 07/05/19 18:20, Cursitor Doom wrote:
On Tue, 07 May 2019 07:14:33 -0700, klaus.kragelund wrote:

Hi

I'm working on my ~3ns 4 diode sampler (preferable 1ns if possible)

I know I'll appear a dinosaur by saying this, but you really can't
beat a
good old fashioned Wien Bridge oscillator when it comes to spectral
purity and low phase noise. They certainly beat the crap out of any
digital synthesis technique IMV.

No, but that statement is about as sensible as almost
all your statements.

He's right about the spectral purity and the phase noise can be cleaned
up by injection-locking it.

A sampler time base needs to stay phase coherent to a trigger.
Injection locking whacks randomly the phase. We care about time, not
frequency.

Sinusoidal injection locking of sinusoidal oscillators is a lot
gentler than square wave injection.

Or any injection that doesn't have much above F_0. The "whack" in square
wave injection comes from the series of odd harmonics, but the actual
locking is achieved by the F_0 component.

Clifford Heath.

Injection locking can be done a lot more gently using parametric effects.

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

 

[John Larkin]

On Sun, 12 May 2019 14:01:13 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 5/9/19 9:55 PM, Clifford Heath wrote:
On 9/5/19 11:33 pm, Phil Hobbs wrote:
On 5/7/19 4:57 PM, John Larkin wrote:
On Tue, 7 May 2019 15:39:04 -0400, bitrex <user@example.net> wrote:

On 5/7/19 3:08 PM, Tom Gardner wrote:
On 07/05/19 18:20, Cursitor Doom wrote:
On Tue, 07 May 2019 07:14:33 -0700, klaus.kragelund wrote:

Hi

I'm working on my ~3ns 4 diode sampler (preferable 1ns if possible)

I know I'll appear a dinosaur by saying this, but you really can't
beat a
good old fashioned Wien Bridge oscillator when it comes to spectral
purity and low phase noise. They certainly beat the crap out of any
digital synthesis technique IMV.

No, but that statement is about as sensible as almost
all your statements.

He's right about the spectral purity and the phase noise can be cleaned
up by injection-locking it.

A sampler time base needs to stay phase coherent to a trigger.
Injection locking whacks randomly the phase. We care about time, not
frequency.

Sinusoidal injection locking of sinusoidal oscillators is a lot
gentler than square wave injection.

Or any injection that doesn't have much above F_0. The "whack" in square
wave injection comes from the series of odd harmonics, but the actual
locking is achieved by the F_0 component.

Clifford Heath.

Injection locking can be done a lot more gently using parametric effects.

Something needs to be nonlinear, which would usually be the natural
amplitude limiting mechanism. In a very linear circuit, with a really
good AGC loop to regulate amplitude, injection locking gets
interesting.

I played with a polyphase phase-lock idea, to start an oscillator and
have it lock to a reference at multiple phase opportunities. That
could be done a number of ways, including injection. Fun but not good
enough.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Bill Sloman]

On Monday, May 13, 2019 at 4:54:25 PM UTC+10, whit3rd wrote:

On Sunday, May 12, 2019 at 11:01:19 AM UTC-7, Phil Hobbs wrote:
On 5/9/19 9:55 PM, Clifford Heath wrote:
On 9/5/19 11:33 pm, Phil Hobbs wrote:
On 5/7/19 4:57 PM, John Larkin wrote:

A sampler time base needs to stay phase coherent to a trigger.
Injection locking whacks randomly the phase. We care about time, not
frequency.

Sinusoidal injection locking of sinusoidal oscillators is a lot
gentler than square wave injection.

Or any injection that doesn't have much above F_0. The "whack" in square
wave injection comes from the series of odd harmonics,...

Injection locking can be done a lot more gently using parametric effects.

The 'gentle' locking wouldn't give a square-wave clock, would it?
For sampling, you don't really WANT a sinewave (zero cross detection
would be a jitter source), but a harmonic-rich signal with sharp
transitions (and well-defined transition times).

The high Q resonators that give stable clock frequencies and good long term jitter only have a high Q at a particular frequency.

If you want to get a square wave clock out of that you have to use a comparator to square it off, with all the added extra noise that that introduces.

Presumably, too, your timebase needs aren't profound in terms
of spectral purity. Sines could be good for timing accuracy, but
not well-adapted to the sample-time requirement of an
abrupt edge.

Tough.

A good overall solution is a squarewave delay-line oscillator with a second
oscillator as a backup. One such can be taking trigger events and producing
samples, while the backup is internally gated for a calibration. Every few
seconds, swap the roles, so you always have a freshly calibrated timebase.

Both of them are low Q oscillators. No amount of calibration is going to make them any quieter.

Regular old CAT5 might not age well as a time standard, but it's
an acceptable delay line (if a TDR can find a break down to a few inches,
the timing jitter must be subnanosecond for the delay). There are other
kinds of delays (piezoelectric/glass-plate like PAL used to use) but not as
easy to damp (terminate) between triggers.

High frequency crystal-based oscillators can offer jitter down to about 125 femtoseconds. That's hard to beat.

> It's not essential to control the timing accurately, just precisely; accuracy can be calibrated in as required.

True, but high-Q oscillators do offer precision and stability.

--
Bill Sloman, Sydney

 

[whit3rd]

On Sunday, May 12, 2019 at 11:01:19 AM UTC-7, Phil Hobbs wrote:

On 5/9/19 9:55 PM, Clifford Heath wrote:
On 9/5/19 11:33 pm, Phil Hobbs wrote:
On 5/7/19 4:57 PM, John Larkin wrote:

A sampler time base needs to stay phase coherent to a trigger.
Injection locking whacks randomly the phase. We care about time, not
frequency.

Sinusoidal injection locking of sinusoidal oscillators is a lot
gentler than square wave injection.

Or any injection that doesn't have much above F_0. The "whack" in square
wave injection comes from the series of odd harmonics,...

Injection locking can be done a lot more gently using parametric effects.

The 'gentle' locking wouldn't give a square-wave clock, would it?
For sampling, you don't really WANT a sinewave (zero cross detection
would be a jitter source), but a harmonic-rich signal with sharp
transitions (and well-defined transition times).

Presumably, too, your timebase needs aren't profound in terms
of spectral purity. Sines could be good for timing accuracy, but
not well-adapted to the sample-time requirement of an
abrupt edge.

A good overall solution is a squarewave delay-line oscillator with a second
oscillator as a backup. One such can be taking trigger events and producing
samples, while the backup is internally gated for a calibration. Every few seconds,
swap the roles, so you always have a freshly calibrated timebase.

Regular old CAT5 might not age well as a time standard, but it's
an acceptable delay line (if a TDR can find a break down to a few inches,
the timing jitter must be subnanosecond for the delay). There are other
kinds of delays (piezoelectric/glass-plate like PAL used to use) but not as easy
to damp (terminate) between triggers.

It's not essential to control the timing accurately, just precisely; accuracy can be
calibrated in as required.

 

[whit3rd]

On Monday, May 13, 2019 at 12:05:39 AM UTC-7, Bill Sloman wrote:

On Monday, May 13, 2019 at 4:54:25 PM UTC+10, whit3rd wrote:
On Sunday, May 12, 2019 at 11:01:19 AM UTC-7, Phil Hobbs wrote:

A sampler time base needs to stay phase coherent to a trigger.
Injection locking whacks randomly the phase. We care about time, not
frequency.

For sampling, you don't really WANT a sinewave (zero cross detection
would be a jitter source), but a harmonic-rich signal with sharp
transitions (and well-defined transition times).

The high Q resonators that give stable clock frequencies and good long term jitter only have a high Q at a particular frequency.

A good overall solution is a squarewave delay-line oscillator with a second
oscillator as a backup. One such can be taking trigger events and producing
samples, while the backup is internally gated for a calibration. Every few
seconds, swap the roles, so you always have a freshly calibrated timebase.

Both of them are low Q oscillators. No amount of calibration is going to make them any quieter.

A delay line has resistor noise associated with its impedance, is that the unquiet aspect?
Or, it's higher (due to skin effect) for the highest harmonics?
The stored-energy model of Q doesn't really clearly fit the delay-line with square
waveform. The jitter comes not from the fundamental, but from sums of harmonics,
so the appropriate energy-input per cycle and stored energy are difficult to infer.

> High frequency crystal-based oscillators can offer jitter down to about 125 femtoseconds. That's hard to beat.

Starting in phase, though, is impossible for a high-Q quartz crystal (and
rather difficult for an LC tank). The various time-vernier schemes have the
same jitter as a monostable (not very good); and the track-hold trick with
multipliers is elaborate and awkward.

 

[Jeroen Belleman]

whit3rd wrote:
[...]

A delay line has resistor noise associated with its impedance, is
that the unquiet aspect?
[...]

Not true. Thermal noise is associated with dissipation, loss.
The characteristic impedance of a transmission line is not
lossy and therefore does not generate noise.

Delay line resonators can have respectable Q values, somewhere
between LC and quartz crystals.

This being usenet, and before anyone jumps on me, I'll
add that the *loss* of practical transmission lines *does*
produce thermal noise.

Jeroen Belleman

 

[Bill Sloman]

On Monday, May 13, 2019 at 9:08:59 PM UTC+10, whit3rd wrote:

On Monday, May 13, 2019 at 12:05:39 AM UTC-7, Bill Sloman wrote:
On Monday, May 13, 2019 at 4:54:25 PM UTC+10, whit3rd wrote:
On Sunday, May 12, 2019 at 11:01:19 AM UTC-7, Phil Hobbs wrote:

A sampler time base needs to stay phase coherent to a trigger.
Injection locking whacks randomly the phase. We care about time, not
frequency.

For sampling, you don't really WANT a sinewave (zero cross detection
would be a jitter source), but a harmonic-rich signal with sharp
transitions (and well-defined transition times).

The high Q resonators that give stable clock frequencies and good long term jitter only have a high Q at a particular frequency.

A good overall solution is a squarewave delay-line oscillator with a second
oscillator as a backup. One such can be taking trigger events and producing
samples, while the backup is internally gated for a calibration. Every few
seconds, swap the roles, so you always have a freshly calibrated timebase.

Both of them are low Q oscillators. No amount of calibration is going to make them any quieter.

A delay line has resistor noise associated with its impedance, is that the
unquiet aspect?
Or, it's higher (due to skin effect) for the highest harmonics?
The stored-energy model of Q doesn't really clearly fit the delay-line with square waveform. The jitter comes not from the fundamental, but from sums of harmonics, so the appropriate energy-input per cycle and stored energy are difficult to infer.

High frequency crystal-based oscillators can offer jitter down to about 125 femtoseconds. That's hard to beat.

Starting in phase, though, is impossible for a high-Q quartz crystal (and
rather difficult for an LC tank). The various time-vernier schemes have the
same jitter as a monostable (not very good); and the track-hold trick with
multipliers is elaborate and awkward.

The timing scheme we used back in 1988 interpolated between 1.25 nsec spaced clock edges. We actually ramped over about 2nsec, and the time jitter was correspondingly small.

Smaller than the 60psec on the clock (which was dire, and would certainly have been improved if we'd ever got to put the machine into production).

When I reworked the design - for another application nearly ten years later - I could buy a thinned-crystal based oscillator with about 1psec jitter.

Back 1988 we were thinking hopefully about a SAW oscillator, but we would have had to buy a small batch of them, and the prototype machine didn't need particularly wonderful jitter performance.

--
Bill Sloman, Sydney

 

[Gerhard Hoffmann]

Am 13.05.19 um 15:27 schrieb Jeroen Belleman:

whit3rd wrote:
[...]
A delay line has resistor noise associated with its impedance, is
that the unquiet aspect?
[...]

Not true. Thermal noise is associated with dissipation, loss.
The characteristic impedance of a transmission line is not
lossy and therefore does not generate noise.

Delay line resonators can have respectable Q values, somewhere
between LC and quartz crystals.

This being usenet, and before anyone jumps on me, I'll
add that the *loss* of practical transmission lines *does*
produce thermal noise.

Jeroen Belleman

completely right.
cheers, Gerhard

 

[John Larkin]

On Mon, 13 May 2019 15:27:16 +0200, Jeroen Belleman
<jeroen@nospam.please> wrote:

whit3rd wrote:
[...]
A delay line has resistor noise associated with its impedance, is
that the unquiet aspect?
[...]

Not true. Thermal noise is associated with dissipation, loss.
The characteristic impedance of a transmission line is not
lossy and therefore does not generate noise.

Delay line resonators can have respectable Q values, somewhere
between LC and quartz crystals.

Coaxial ceramic resonators are short, high dielectric, usually shorted
transmission lines. The lower frequency parts (below say 1 GHz) have
Qs in the hundreds, and the higher ones in the thousands. Temperature
stability is astounding.

This being usenet, and before anyone jumps on me, I'll
add that the *loss* of practical transmission lines *does*
produce thermal noise.

CCR characteristic impedances are low, ca 10 ohms, and their DC
resistances are milliohms. Like most RF parts, they are characterized
in frequency domain, but they really are transmission lines.

https://www.dropbox.com/s/01cgtptkztpfyga/CCR_600.JPG?dl=0

https://www.dropbox.com/s/19imyfg1ubh2z3c/P5_CCRO.jpg?dl=0

Jeroen Belleman

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[John Larkin]

On Mon, 13 May 2019 04:08:54 -0700 (PDT), whit3rd <whit3rd@gmail.com>
wrote:

On Monday, May 13, 2019 at 12:05:39 AM UTC-7, Bill Sloman wrote:
On Monday, May 13, 2019 at 4:54:25 PM UTC+10, whit3rd wrote:
On Sunday, May 12, 2019 at 11:01:19 AM UTC-7, Phil Hobbs wrote:

A sampler time base needs to stay phase coherent to a trigger.
Injection locking whacks randomly the phase. We care about time, not
frequency.

For sampling, you don't really WANT a sinewave (zero cross detection
would be a jitter source), but a harmonic-rich signal with sharp
transitions (and well-defined transition times).

The high Q resonators that give stable clock frequencies and good long term jitter only have a high Q at a particular frequency.

A good overall solution is a squarewave delay-line oscillator with a second
oscillator as a backup. One such can be taking trigger events and producing
samples, while the backup is internally gated for a calibration. Every few
seconds, swap the roles, so you always have a freshly calibrated timebase.

Both of them are low Q oscillators. No amount of calibration is going to make them any quieter.

A delay line has resistor noise associated with its impedance, is that the unquiet aspect?
Or, it's higher (due to skin effect) for the highest harmonics?

Higher harmonics generally have lower Q, so delay line oscillators
tend to settle down to making sine waves.

The stored-energy model of Q doesn't really clearly fit the delay-line with square
waveform. The jitter comes not from the fundamental, but from sums of harmonics,
so the appropriate energy-input per cycle and stored energy are difficult to infer.

High frequency crystal-based oscillators can offer jitter down to about 125 femtoseconds. That's hard to beat.

Starting in phase, though, is impossible for a high-Q quartz crystal (and
rather difficult for an LC tank).

It's tough for the crystal because it's a complex mechanical device
with weak coupling to the outside world. The LC instant start is
trivial; first semister EE or calculus.

HP sold a digital delay generator, for a while, that instant-started a
quartz crystal oscillator. It was ugly.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Phil Hobbs]

On 5/13/19 2:54 AM, whit3rd wrote:

On Sunday, May 12, 2019 at 11:01:19 AM UTC-7, Phil Hobbs wrote:
On 5/9/19 9:55 PM, Clifford Heath wrote:
On 9/5/19 11:33 pm, Phil Hobbs wrote:
On 5/7/19 4:57 PM, John Larkin wrote:

A sampler time base needs to stay phase coherent to a trigger.
Injection locking whacks randomly the phase. We care about time, not
frequency.

Sinusoidal injection locking of sinusoidal oscillators is a lot
gentler than square wave injection.

Or any injection that doesn't have much above F_0. The "whack" in square
wave injection comes from the series of odd harmonics,...

Injection locking can be done a lot more gently using parametric effects.

The 'gentle' locking wouldn't give a square-wave clock, would it?
For sampling, you don't really WANT a sinewave (zero cross detection
would be a jitter source), but a harmonic-rich signal with sharp
transitions (and well-defined transition times).

You can do zero-cross detection by amplifying and clipping.

The math of injection locking is fascinating--it's full of bifurcations
and limit cycles and stuff. Sure works if you get it right, 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