Phase Noise vs. Jitter

[Cursitor Doom]

Gentlemen,

I thought these terms were effectively the same thing, but now I'm not so
sure.
Taking a square waveform of uniform amplitude for the sake of simplicity,
AFAIAA, if I'm looking at such a wave in the time domain with an
oscilloscope and I'm seeing intermittent thickening of the vertical
portions of the trace, that's jitter. But if the frequency of the wave is
more slowly varying, then that's phase noise, which can be observed with
a spectrum analyser (frequency domain) as the presence of unwanted
sidebands on what would be an otherwise infinitely thin vertical peak if
the wave had perfect spectral purity. Do I have that right?
<cue massive argument, probably>

TIA



--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

 

On Sun, 15 Sep 2019 00:25:46 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

Gentlemen,

I thought these terms were effectively the same thing, but now I'm not so
sure.
Taking a square waveform of uniform amplitude for the sake of simplicity,
AFAIAA, if I'm looking at such a wave in the time domain with an
oscilloscope and I'm seeing intermittent thickening of the vertical
portions of the trace, that's jitter. But if the frequency of the wave is
more slowly varying, then that's phase noise, which can be observed with
a spectrum analyser (frequency domain) as the presence of unwanted
sidebands on what would be an otherwise infinitely thin vertical peak if
the wave had perfect spectral purity. Do I have that right?
cue massive argument, probably

TIA

There's a math operation that maps one into the other, at least for
wideband noise and RMS jitter. There are several calculators online.

One of the guys here did this:

https://www.dropbox.com/s/zkhw9nlkwurcy7q/PhaseNoise102.exe?dl=0

In the telecom business, stuff below 0.1 Hz is called "wander" and
faster wiggles are "jitter."

 

[Rick C]

On Saturday, September 14, 2019 at 8:25:51 PM UTC-4, Cursitor Doom wrote:

Gentlemen,

I thought these terms were effectively the same thing, but now I'm not so
sure.
Taking a square waveform of uniform amplitude for the sake of simplicity,
AFAIAA, if I'm looking at such a wave in the time domain with an
oscilloscope and I'm seeing intermittent thickening of the vertical
portions of the trace, that's jitter. But if the frequency of the wave is
more slowly varying, then that's phase noise, which can be observed with
a spectrum analyser (frequency domain) as the presence of unwanted
sidebands on what would be an otherwise infinitely thin vertical peak if
the wave had perfect spectral purity. Do I have that right?
cue massive argument, probably

TIA



--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

What you seem to be talking about is like the old turntables which has specs for "wow" and "flutter". One was fast and the other slow. Same but different. Or not so different really, they just produced different effects on the sound and usually had different causes, but both are just variations in the speed of the platter.

Likewise your jitter and phase noise are the same thing, just different parts of the frequency spectrum. Same but different.

Why do you care exactly? How are you using this?

--

Rick C.

- Get 2,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

 

[Bill Sloman]

On Sunday, September 15, 2019 at 2:08:22 PM UTC+10, Rick C wrote:

On Saturday, September 14, 2019 at 8:25:51 PM UTC-4, Cursitor Doom wrote:
Gentlemen,

I thought these terms were effectively the same thing, but now I'm not so
sure.
Taking a square waveform of uniform amplitude for the sake of simplicity,
AFAIAA, if I'm looking at such a wave in the time domain with an
oscilloscope and I'm seeing intermittent thickening of the vertical
portions of the trace, that's jitter. But if the frequency of the wave is
more slowly varying, then that's phase noise, which can be observed with
a spectrum analyser (frequency domain) as the presence of unwanted
sidebands on what would be an otherwise infinitely thin vertical peak if
the wave had perfect spectral purity. Do I have that right?
cue massive argument, probably

TIA



--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

What you seem to be talking about is like the old turntables which has specs for "wow" and "flutter". One was fast and the other slow. Same but different. Or not so different really, they just produced different effects on the sound and usually had different causes, but both are just variations in the speed of the platter.

Likewise your jitter and phase noise are the same thing, just different parts of the frequency spectrum. Same but different.

Why do you care exactly? How are you using this?

Actually "jitter" is variation in period, and is measured once per period, and phase noise is variation from an ideal - perfectly regular - waveform and is integrated over the whole period.

It's not always a particularly useful distinction, but Cursitor Doom doesn't think about what he's doing.

--
Bill Sloman, Sydney

 

[Cursitor Doom]

On Sat, 14 Sep 2019 20:06:46 -0700, jlarkin wrote:

There's a math operation that maps one into the other, at least for
wideband noise and RMS jitter. There are several calculators online.

I don't want a mathematical explanation, though; just an intuitive one.

In the telecom business, stuff below 0.1 Hz is called "wander" and
faster wiggles are "jitter."

In that case I've discovered a new phenomenon I've dubbed "twitch".

"Exe files can't be previewed" it says on your link.

Let's try re-phrasing it thus: phase noise produces sidebands. Does
jitter?



--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

 

[Cursitor Doom]

On Sat, 14 Sep 2019 21:08:18 -0700, Rick C wrote:

> Why do you care exactly? How are you using this?

A recent acquaintance of mine has built some fancy super-fast (to me)
oscillator which he wants to hook up to one of my SAs to check for
stability and purity. I don't want to look an ass if he asks me something
technical that's above my pay-grade and as a mere hobbyist, my-pay grade
is pretty low.



--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

 

[Bill Sloman]

On Sunday, September 15, 2019 at 7:14:27 PM UTC+10, Cursitor Doom wrote:

On Sat, 14 Sep 2019 20:06:46 -0700, jlarkin wrote:

There's a math operation that maps one into the other, at least for
wideband noise and RMS jitter. There are several calculators online.

I don't want a mathematical explanation, though; just an intuitive one.

Something dumbed down enough for Cursitor Doom to understand.

In the telecom business, stuff below 0.1 Hz is called "wander" and
faster wiggles are "jitter."

In that case I've discovered a new phenomenon I've dubbed "twitch".

"Exe files can't be previewed" it says on your link.

Let's try re-phrasing it thus: phase noise produces sidebands. Does
jitter?

The kind of deviations from the ideal perfectly repetitive waveform that constitute phase noise, and can be characterised as jitter, show up as low level sidebands on the Fourier transform of a noisy and jittery waveform.

--
Bill Sloman, Sydney

 

Bill Sloman <bill.sloman@ieee.org> wrote in
news:b12adec6-6c84-438b-877c-f010a60b8106@googlegroups.com:

On Sunday, September 15, 2019 at 7:14:27 PM UTC+10, Cursitor Doom
wrote:
On Sat, 14 Sep 2019 20:06:46 -0700, jlarkin wrote:

There's a math operation that maps one into the other, at least
for wideband noise and RMS jitter. There are several
calculators online.

I don't want a mathematical explanation, though; just an
intuitive one.

Something dumbed down enough for Cursitor Doom to understand.

In the telecom business, stuff below 0.1 Hz is called "wander"
and faster wiggles are "jitter."

In that case I've discovered a new phenomenon I've dubbed
"twitch".

"Exe files can't be previewed" it says on your link.

Let's try re-phrasing it thus: phase noise produces sidebands.
Does jitter?

The kind of deviations from the ideal perfectly repetitive
waveform that constitute phase noise, and can be characterised as
jitter, show up as low level sidebands on the Fourier transform of
a noisy and jittery waveform.

clock jitter.

<https://about.keysight.com/en/newsroom/imagelibrary/2006/02may-
em06067/>

<https://about.keysight.com/en/newsroom/imagelibrary/2006/02may-
em06067/image001.jpg>

 

Bill Sloman <bill.sloman@ieee.org> wrote in
news:ac91c001-a3a0-4aa6-8243-f600aa23c606@googlegroups.com:

On Sunday, September 15, 2019 at 2:08:22 PM UTC+10, Rick C wrote:
On Saturday, September 14, 2019 at 8:25:51 PM UTC-4, Cursitor
Doom wrote:
Gentlemen,

I thought these terms were effectively the same thing, but now
I'm not
so
sure.
Taking a square waveform of uniform amplitude for the sake of
simplicit
y,
AFAIAA, if I'm looking at such a wave in the time domain with
an oscilloscope and I'm seeing intermittent thickening of the
vertical portions of the trace, that's jitter. But if the
frequency of the wave
is
more slowly varying, then that's phase noise, which can be
observed wit
h
a spectrum analyser (frequency domain) as the presence of
unwanted sidebands on what would be an otherwise infinitely
thin vertical peak i
f
the wave had perfect spectral purity. Do I have that right?
cue massive argument, probably

TIA



--
This message may be freely reproduced without limit or charge
only via

the Usenet protocol. Reproduction in whole or part through
other protocols, whether for profit or not, is conditional upon
a charge of

GBP10.00 per reproduction. Publication in this manner via
non-Usenet protocols constitutes acceptance of this condition.

What you seem to be talking about is like the old turntables
which has sp
ecs for "wow" and "flutter". One was fast and the other slow.
Same but different. Or not so different really, they just
produced different effects on the sound and usually had different
causes, but both are just variations in the speed of the platter.

Likewise your jitter and phase noise are the same thing, just
different p
arts of the frequency spectrum. Same but different.

Why do you care exactly? How are you using this?

Actually "jitter" is variation in period, and is measured once per
period, and phase noise is variation from an ideal - perfectly
regular - waveform and is integrated over the whole period.

It's not always a particularly useful distinction, but Cursitor
Doom doesn't think about what he's doing.

<https://www.keysight.com/upload/cmc_upload/All/PhaseNoise_webcast19J
ul12.pdf>

A really good piece on it.

 

On Sun, 15 Sep 2019 09:14:23 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

On Sat, 14 Sep 2019 20:06:46 -0700, jlarkin wrote:

There's a math operation that maps one into the other, at least for
wideband noise and RMS jitter. There are several calculators online.

I don't want a mathematical explanation, though; just an intuitive one.

In the telecom business, stuff below 0.1 Hz is called "wander" and
faster wiggles are "jitter."

In that case I've discovered a new phenomenon I've dubbed "twitch".

"Exe files can't be previewed" it says on your link.

Download it and run it. It's cool and perfectly safe.

Let's try re-phrasing it thus: phase noise produces sidebands. Does
jitter?

Sure. If the period of a signal isn't exactly constant, then it's
frequency is being modulated. And FM makes spectral components in
addition to the main frequency spike.

If the jitter is fast and random, the frequency-domain noise floor is
wideband, so a spectrum analyzer might not show classic sidebands,
just an elevated noise floor. But some kind of systematic jitter, like
time wobble caused by power supply ripple, will make classic looking
sidebands around the main frequency line; FM.

I often measure jitter as a function of time. The shortest time is a
single cycle of a waveform, which is what you usually see on a scope.
But you can measure one rising edge relative to the 10th edge away, or
the millionth one. A graph of jitter vs time correlates directly with
the phase noise graph of the oscillator. Low frequency phase noise
makes long-timebase jitter. You can, in theory, measure the jitter of
a 1-year time delay; it will be huge.

A cheap crystal oscillator will have maybe 10 nanoseconds of RMS
jitter when it's used to time out one second of delay. A really good
OCXO will have a few picoseconds. The phase noise plots are indicators
of the jitter behavior.

Allan variance is one formal way of expressing the complex phase
noise/jitter of an oscillator.

 

On Sun, 15 Sep 2019 09:08:53 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

On Sat, 14 Sep 2019 21:08:18 -0700, Rick C wrote:

Why do you care exactly? How are you using this?

A recent acquaintance of mine has built some fancy super-fast (to me)
oscillator which he wants to hook up to one of my SAs to check for
stability and purity. I don't want to look an ass if he asks me something
technical that's above my pay-grade and as a mere hobbyist, my-pay grade
is pretty low.

What kind of resonator is he using? An LC or equivalent will probably
show lots of sideband junk on a decent spectrum analyzer. Some really
good ones could wind up displaying the phase noise of the SA itself.

Check for harmonics too, just for fun. Even some high-end, supposedly
low phase noise, signal generators have horrible harmonics.

Look for line-frequency sidebands too. The moral equivalent of roaches
in the soup.

Post a spectrum pic here, if you can.

 

[Cursitor Doom]

On Sun, 15 Sep 2019 08:17:08 -0700, jlarkin wrote:

[...]

Thanks, John. That's exactly the clear explanation I was looking for. Now
watch some awkward bastard come along and find fault with it.



--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

 

[Cursitor Doom]

On Sun, 15 Sep 2019 08:24:08 -0700, jlarkin wrote:

> What kind of resonator is he using?

No idea as yet.

An LC or equivalent will probably
show lots of sideband junk on a decent spectrum analyzer. Some really
good ones could wind up displaying the phase noise of the SA itself.

I'd be surprised. The guy is a heavy-duty scientist in his own field and
retired from various blue chip pharmaceutical gigs, but just a hobbyist
(albeit advanced) like me in electronics.

Check for harmonics too, just for fun. Even some high-end, supposedly
low phase noise, signal generators have horrible harmonics.

I have no SA that goes beyond 22Ghz without deploying some external
source which would take it/them up to just above 40, and as yet I have no
idea what frequency his fundamental is even. I'm sure 40Ghz is
practically DC for a bloke of your calibre and worthy of haughty
derision.

Look for line-frequency sidebands too. The moral equivalent of roaches
in the soup.

From the mains power you mean? Not much chance of that. Min sweep starts
at 10Mhz.

> Post a spectrum pic here, if you can.

Might take a couple of weeks before we can meet up and perform the
relevant tests but I'll post back with pics if I can.



--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

 

On Sun, 15 Sep 2019 16:08:54 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

On Sun, 15 Sep 2019 08:24:08 -0700, jlarkin wrote:

What kind of resonator is he using?

No idea as yet.

An LC or equivalent will probably
show lots of sideband junk on a decent spectrum analyzer. Some really
good ones could wind up displaying the phase noise of the SA itself.

I'd be surprised. The guy is a heavy-duty scientist in his own field and
retired from various blue chip pharmaceutical gigs, but just a hobbyist
(albeit advanced) like me in electronics.

Check for harmonics too, just for fun. Even some high-end, supposedly
low phase noise, signal generators have horrible harmonics.

I have no SA that goes beyond 22Ghz without deploying some external
source which would take it/them up to just above 40, and as yet I have no
idea what frequency his fundamental is even. I'm sure 40Ghz is
practically DC for a bloke of your calibre and worthy of haughty
derision.

Not really. We're time domain, not RF. I did recently do some
low-phase-noise VCOs with coaxial ceramic resonators, around 600 MHz.
And a triggered LC oscillator at 40 MHz.

https://www.dropbox.com/s/5z3lgsovd7yqr9y/Trig_Osc_40M.jpg?raw=1

Look for line-frequency sidebands too. The moral equivalent of roaches
in the soup.

From the mains power you mean? Not much chance of that. Min sweep starts
at 10Mhz.

Could have close-in sidebands, +- 60 or 120 Hz from the main line.

Post a spectrum pic here, if you can.

Might take a couple of weeks before we can meet up and perform the
relevant tests but I'll post back with pics if I can.

 

[John Larkin]

On Sun, 15 Sep 2019 09:08:53 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

On Sat, 14 Sep 2019 21:08:18 -0700, Rick C wrote:

Why do you care exactly? How are you using this?

A recent acquaintance of mine has built some fancy super-fast (to me)
oscillator which he wants to hook up to one of my SAs to check for
stability and purity. I don't want to look an ass if he asks me something
technical that's above my pay-grade and as a mere hobbyist, my-pay grade
is pretty low.

Oh, ricky and sloman are both wrong. Jitter is a time-domain
measurement, and phase noise is frequency domain. Either can be mapped
into the other mathematically, but the units and measurement are
different.

And jitter is not just a single-period measurement. Low frequency
phase noise causes long-interval jitter.

 

[John Larkin]

On Sun, 15 Sep 2019 15:29:03 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

On Sun, 15 Sep 2019 08:17:08 -0700, jlarkin wrote:

[...]

Thanks, John. That's exactly the clear explanation I was looking for. Now
watch some awkward bastard come along and find fault with it.

One fun thing is spread-spectrum switching regulators. They jitter
hard in time domain, to spread out the RF spectrum and pass FCC
limits. It is sort of cheating.

https://www.dropbox.com/s/s9aqx1z3glab423/TPS54302_PWM.JPG?raw=1

It surprised me that the DC output is very quiet. They must shape the
timing of the jitter, like a 2nd order delta-sigma modulator, to push
the noise spectrum up where the output filter kills it.

 

[Rick C]

On Sunday, September 15, 2019 at 5:08:58 AM UTC-4, Cursitor Doom wrote:

On Sat, 14 Sep 2019 21:08:18 -0700, Rick C wrote:

Why do you care exactly? How are you using this?

A recent acquaintance of mine has built some fancy super-fast (to me)
oscillator which he wants to hook up to one of my SAs to check for
stability and purity. I don't want to look an ass if he asks me something
technical that's above my pay-grade and as a mere hobbyist, my-pay grade
is pretty low.

I like when people ask me questions above my pay grade. I ask them to explain what they are talking about. That's when things get interesting.

--

Rick C.

+ Get 2,000 miles of free Supercharging
+ Tesla referral code - https://ts.la/richard11209

 

[Bill Sloman]

On Tuesday, September 17, 2019 at 4:26:02 AM UTC+10, John Larkin wrote:

On Sun, 15 Sep 2019 09:08:53 -0000 (UTC), Cursitor Doom
curd@notformail.com> wrote:

On Sat, 14 Sep 2019 21:08:18 -0700, Rick C wrote:

Why do you care exactly? How are you using this?

A recent acquaintance of mine has built some fancy super-fast (to me)
oscillator which he wants to hook up to one of my SAs to check for
stability and purity. I don't want to look an ass if he asks me something
technical that's above my pay-grade and as a mere hobbyist, my-pay grade
is pretty low.

Oh, ricky and sloman are both wrong. Jitter is a time-domain
measurement, and phase noise is frequency domain. Either can be mapped
into the other mathematically, but the units and measurement are
different.

And where did I say anything else?

And jitter is not just a single-period measurement. Low frequency
phase noise causes long-interval jitter.

"Jitter" is obviously not a single period measurement. You got to take at least two period measurements before you've got a base period to jitter from.

John Larkin tries to do analytical comment, but can't get to first base.

--
Bill Sloman, Sydney

 

[Cursitor Doom]

On Mon, 16 Sep 2019 11:25:52 -0700, John Larkin wrote:

Oh, ricky and sloman are both wrong. Jitter is a time-domain
measurement, and phase noise is frequency domain. Either can be mapped
into the other mathematically, but the units and measurement are
different.

And jitter is not just a single-period measurement. Low frequency phase
noise causes long-interval jitter.

Well, Sloman of all people I would have expected to know that, given it's
the only subject he's professed any qualification in. Perhaps he'll be
along in a minute or two to clarify what he meant. Pity I won't see it if
he does.



--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

 

[Bill Sloman]

On Tuesday, September 17, 2019 at 6:21:37 PM UTC+10, Cursitor Doom wrote:

On Mon, 16 Sep 2019 11:25:52 -0700, John Larkin wrote:

Oh, ricky and sloman are both wrong. Jitter is a time-domain
measurement, and phase noise is frequency domain. Either can be mapped
into the other mathematically, but the units and measurement are
different.

And jitter is not just a single-period measurement. Low frequency phase
noise causes long-interval jitter.

Well, Sloman of all people I would have expected to know that, given it's
the only subject he's professed any qualification in. Perhaps he'll be
along in a minute or two to clarify what he meant. Pity I won't see it if
he does.

John Larkin clearly doesn't know what he's talking about. I've never suggested that jitter was a single period measurement. The idea is absurd.

Cursitor Doom is similarly inane. I've never "professed" to have any qualifications in electronics - I've never followed any academic course that might have lead to any such qualification.

This hasn't stopped me from working as a high level electronic engineer, or becoming a life senior member of the IEEE.

Cursitor Doom does have his blind spots - his habit of plonking people who point out when he's talking nonsense does mean that he's not reminded that he's talking nonsense quite as often as he might be - but this is sillier than usual.

--
Bill Sloman, Sydney