Reply by Phil Hobbs May 13, 20192019-05-13
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
Reply by John Larkin May 13, 20192019-05-13
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
Reply by John Larkin May 13, 20192019-05-13
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
Reply by Bill Sloman May 13, 20192019-05-13
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
Reply by Gerhard Hoffmann May 13, 20192019-05-13
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
Reply by Jeroen Belleman May 13, 20192019-05-13
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
Reply by whit3rd May 13, 20192019-05-13
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.
Reply by Bill Sloman May 13, 20192019-05-13
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
Reply by whit3rd May 13, 20192019-05-13
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.
Reply by John Larkin May 12, 20192019-05-12
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