Re: [time-nuts] AM vs PM noise of signal sources
On Fri, 05 Jan 2018 12:00:01 -0500, time-nuts-request@febo.com wrote:
Send time-nuts mailing list submissions to
time-nuts@febo.com
To subscribe or unsubscribe via the World Wide Web, visit
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
or, via email, send a message with subject or body 'help' to
time-nuts-request@febo.com
You can reach the person managing the list at
time-nuts-owner@febo.com
When replying, please edit your Subject line so it is more specific
than "Re: Contents of time-nuts digest..."
Today's Topics:
1. Re: Stable32 now available (Graham)
2. Re: Stable32 now available (Dr. David Kirkby)
3. Re: AM vs PM noise of signal sources (Bob kb8tq)
4. HP 105B: Modern replacement for NiCad battery pack?
(Ulf Kylenfall)
Message: 3
Date: Fri, 5 Jan 2018 10:56:17 -0500
From: Bob kb8tq kb8tq@n1k.org
To: Discussion of precise time and frequency measurement
time-nuts@febo.com
Subject: Re: [time-nuts] AM vs PM noise of signal sources
Message-ID: F69F7893-AE69-4430-BAFA-752746BD0CB3@n1k.org
Content-Type: text/plain; charset=utf-8
Hi
If I pass both a sine wave tone and a pile of audio noise through a
perfectly
linear circuit, I get no AM or PM noise sidebands on the signal. The
only way
they combine is if the circuit is non-linear. There are a lot of ways
to model
this non-linearity. The “old school” approach is with a polynomial
function. That
dates back at least into the 1930’s. The textbooks I used learning it
in the 1970’s
were written in the 1950’s. There are many decades of papers on
this stuff.
Simple answer is that some types of non-linearity transfer AM others
transfer PM.
Some transfer both. In some cases the spectrum of the modulation is
preserved.
In some cases the spectrum is re-shaped by the modulation process. As
I recall
we spend a semester going over the basics of what does what.
These days, you have the wonders of non-linear circuit analysis. To
the degree
that your models are accurate and that the methods used work, I’m
sure it will
give you similar data compared to the “old school” stuff.
All the points about the need for linearity are correct. The best
point of access to the math of phase noise (both AM and PM) is
modulation theory - phase noise is low-index modulation of the RF
carrier signal. Given the very low modulation index, only the first
term of the approximating Bessel series is significant. The difference
between AM and PM is the relative phasing of the modulation sidebands.
Additive npose has no such phase relationship.
Joe Gwinn
Bob
On Jan 5, 2018, at 6:27 AM, Attila Kinali attila@kinali.ch wrote:
On Tue, 2 Jan 2018 23:34:18 +0100
Magnus Danielson magnus@rubidium.dyndns.org wrote:[About AM noise being of equal power as PM noise]
Now, for actual sources this is no longer true. The AM noise can be much
higher, which is why it can be a real danger to the PM noise if there is
a AM to PM noise conversion. One source of such conversion can be the
amplification stage, but another could be a mistuned filter, which have
different amplitudes of the side-bands, which can create conversion as
the balance does not balance the same way anymore.Yes, exactly. I am currently trying to understand how noise affects
circuits an how input and circuit noise get converted to output noise.
First assumption that needs to be dropped is that the noise processes
is purely additive and independent of the signal. This means that a
noise process does not anymore produce equal AM and PM power.I think I have a 90% solution of the noise processes and conversions
in a sine-to-square converter (aka zero-crossing detector, aka comparator).
But there is one process that keeps puzzling me. I think I know where in
the circuit it must come from, but I have no explanation as to how
it happens.Attila Kinali--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
End of time-nuts Digest, Vol 162, Issue 7
Joseph,
On 01/05/2018 09:16 PM, Joseph Gwinn wrote:
On Fri, 05 Jan 2018 12:00:01 -0500, time-nuts-request@febo.com wrote:
Send time-nuts mailing list submissions to
If I pass both a sine wave tone and a pile of audio noise through a
perfectly
linear circuit, I get no AM or PM noise sidebands on the signal. The
only way
they combine is if the circuit is non-linear. There are a lot of ways
to model
this non-linearity. The “old school” approach is with a polynomial
function. That
dates back at least into the 1930’s. The textbooks I used learning it
in the 1970’s
were written in the 1950’s. There are many decades of papers on
this stuff.
Simple answer is that some types of non-linearity transfer AM others
transfer PM.
Some transfer both. In some cases the spectrum of the modulation is
preserved.
In some cases the spectrum is re-shaped by the modulation process. As
I recall
we spend a semester going over the basics of what does what.
These days, you have the wonders of non-linear circuit analysis. To
the degree
that your models are accurate and that the methods used work, I’m
sure it will
give you similar data compared to the “old school” stuff.
All the points about the need for linearity are correct. The best
point of access to the math of phase noise (both AM and PM) is
modulation theory - phase noise is low-index modulation of the RF
carrier signal. Given the very low modulation index, only the first
term of the approximating Bessel series is significant. The difference
between AM and PM is the relative phasing of the modulation sidebands.
Additive npose has no such phase relationship.
May I just follow up on the assumption there. The Bessel series is the
theoretical for what goes on in PM and also helps to explain one
particular error I have seen. For one oscillator with particular bad
noise, a commercial instruments gave positive PM nummbers. Rather than
measuring the power of the signal, it measured the power of the carrier.
Under the assumption of low index modulation the Bessel for the carrier
is very close to 1, so it is fairly safe assumption. However, for higher
index the carrier suppresses, and that matches that the Bessel becomes
lower. That's what happen, so a read-out of the carrier is no longer
representing the power of the signal.
However, if you do have low index modulation, you can assume the center
carrier to be as close to full power as you want, and the two
side-carriers has a very simple linear approximation.
Cheers,
Magnus
So to be lowest noise, an oscillator should have the highest Q resonator
possible in its feedback loop, operate in class "A" [for maximum
linearity], and utilise active amplifier device(s) that contribute the
least noise [both amplitude, or 1/f], and phase. This latter implies
operating the active device at maximum output level [ie signal to noise].
The quality of the power supply effects the amplifier SNR, so in the
persuit of superlative oscillator phase noise, the power supply should be
as good as possible.
Resistors in the oscillator carrying DC make 1/f noise - the best in this
respect are the metal type, I think - so use metal resistors or WW.
What are the other conciderations that come into the design, for lowest
noise of the oscillator itself
Split, then
lump...;-).................................................Cheers, de : Don
ZL4GX
http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail
Virus-free.
www.avg.com
http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail
<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
On Sat, Jan 6, 2018 at 1:08 PM, Magnus Danielson <magnus@rubidium.dyndns.org
wrote:
Joseph,
On 01/05/2018 09:16 PM, Joseph Gwinn wrote:
On Fri, 05 Jan 2018 12:00:01 -0500, time-nuts-request@febo.com wrote:
Send time-nuts mailing list submissions to
If I pass both a sine wave tone and a pile of audio noise through a
perfectly
linear circuit, I get no AM or PM noise sidebands on the signal. The
only way
they combine is if the circuit is non-linear. There are a lot of ways
to model
this non-linearity. The “old school” approach is with a polynomial
function. That
dates back at least into the 1930’s. The textbooks I used learning it
in the 1970’s
were written in the 1950’s. There are many decades of papers on
this stuff.
Simple answer is that some types of non-linearity transfer AM others
transfer PM.
Some transfer both. In some cases the spectrum of the modulation is
preserved.
In some cases the spectrum is re-shaped by the modulation process. As
I recall
we spend a semester going over the basics of what does what.
These days, you have the wonders of non-linear circuit analysis. To
the degree
that your models are accurate and that the methods used work, I’m
sure it will
give you similar data compared to the “old school” stuff.
All the points about the need for linearity are correct. The best
point of access to the math of phase noise (both AM and PM) is
modulation theory - phase noise is low-index modulation of the RF
carrier signal. Given the very low modulation index, only the first
term of the approximating Bessel series is significant. The difference
between AM and PM is the relative phasing of the modulation sidebands.
Additive npose has no such phase relationship.
May I just follow up on the assumption there. The Bessel series is the
theoretical for what goes on in PM and also helps to explain one
particular error I have seen. For one oscillator with particular bad
noise, a commercial instruments gave positive PM nummbers. Rather than
measuring the power of the signal, it measured the power of the carrier.
Under the assumption of low index modulation the Bessel for the carrier
is very close to 1, so it is fairly safe assumption. However, for higher
index the carrier suppresses, and that matches that the Bessel becomes
lower. That's what happen, so a read-out of the carrier is no longer
representing the power of the signal.
However, if you do have low index modulation, you can assume the center
carrier to be as close to full power as you want, and the two
side-carriers has a very simple linear approximation.
Cheers,
Magnus
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
Hi
The key point missing is the fact that any real oscillator must have a limiter
in the loop. Otherwise it will “create one” by going over the max output of this or
that amplifier. To the degree that the limiter has issues (limits poorly) you will get
AM noise.
On a practical basis, loop Q is as significant as resonator Q . The various
elements in the loop degrade the total Q by a significant amount. Getting 25 to
50% of the resonator Q is “doing well” with his or that common circuit. Yes, there
are even more layers past this ….
Bob
On Jan 6, 2018, at 1:53 AM, donald collie donaldbcollie@gmail.com wrote:
So to be lowest noise, an oscillator should have the highest Q resonator
possible in its feedback loop, operate in class "A" [for maximum
linearity], and utilise active amplifier device(s) that contribute the
least noise [both amplitude, or 1/f], and phase. This latter implies
operating the active device at maximum output level [ie signal to noise].
The quality of the power supply effects the amplifier SNR, so in the
persuit of superlative oscillator phase noise, the power supply should be
as good as possible.
Resistors in the oscillator carrying DC make 1/f noise - the best in this
respect are the metal type, I think - so use metal resistors or WW.
What are the other conciderations that come into the design, for lowest
noise of the oscillator itself
Split, then
lump...;-).................................................Cheers, de : Don
ZL4GX
http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail
Virus-free.
www.avg.com
http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail
<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
On Sat, Jan 6, 2018 at 1:08 PM, Magnus Danielson <magnus@rubidium.dyndns.org
wrote:
Joseph,
On 01/05/2018 09:16 PM, Joseph Gwinn wrote:
On Fri, 05 Jan 2018 12:00:01 -0500, time-nuts-request@febo.com wrote:
Send time-nuts mailing list submissions to
If I pass both a sine wave tone and a pile of audio noise through a
perfectly
linear circuit, I get no AM or PM noise sidebands on the signal. The
only way
they combine is if the circuit is non-linear. There are a lot of ways
to model
this non-linearity. The “old school” approach is with a polynomial
function. That
dates back at least into the 1930’s. The textbooks I used learning it
in the 1970’s
were written in the 1950’s. There are many decades of papers on
this stuff.
Simple answer is that some types of non-linearity transfer AM others
transfer PM.
Some transfer both. In some cases the spectrum of the modulation is
preserved.
In some cases the spectrum is re-shaped by the modulation process. As
I recall
we spend a semester going over the basics of what does what.
These days, you have the wonders of non-linear circuit analysis. To
the degree
that your models are accurate and that the methods used work, I’m
sure it will
give you similar data compared to the “old school” stuff.
All the points about the need for linearity are correct. The best
point of access to the math of phase noise (both AM and PM) is
modulation theory - phase noise is low-index modulation of the RF
carrier signal. Given the very low modulation index, only the first
term of the approximating Bessel series is significant. The difference
between AM and PM is the relative phasing of the modulation sidebands.
Additive npose has no such phase relationship.
May I just follow up on the assumption there. The Bessel series is the
theoretical for what goes on in PM and also helps to explain one
particular error I have seen. For one oscillator with particular bad
noise, a commercial instruments gave positive PM nummbers. Rather than
measuring the power of the signal, it measured the power of the carrier.
Under the assumption of low index modulation the Bessel for the carrier
is very close to 1, so it is fairly safe assumption. However, for higher
index the carrier suppresses, and that matches that the Bessel becomes
lower. That's what happen, so a read-out of the carrier is no longer
representing the power of the signal.
However, if you do have low index modulation, you can assume the center
carrier to be as close to full power as you want, and the two
side-carriers has a very simple linear approximation.
Cheers,
Magnus
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Hi,
I think loaded Q is being used as term these days for the effective Q of
the resonator as loaded by the support amplifier.
The Leeson model only models how noise types gets created, not how a
physical design actually works.
The modified Leeson model starts to approach the actual design.
Cheers,
Magnus
On 01/06/2018 03:19 PM, Bob kb8tq wrote:
Hi
The key point missing is the fact that any real oscillator must have a limiter
in the loop. Otherwise it will “create one” by going over the max output of this or
that amplifier. To the degree that the limiter has issues (limits poorly) you will get
AM noise.
On a practical basis, loop Q is as significant as resonator Q . The various
elements in the loop degrade the total Q by a significant amount. Getting 25 to
50% of the resonator Q is “doing well” with his or that common circuit. Yes, there
are even more layers past this ….
Bob
On Jan 6, 2018, at 1:53 AM, donald collie donaldbcollie@gmail.com wrote:
So to be lowest noise, an oscillator should have the highest Q resonator
possible in its feedback loop, operate in class "A" [for maximum
linearity], and utilise active amplifier device(s) that contribute the
least noise [both amplitude, or 1/f], and phase. This latter implies
operating the active device at maximum output level [ie signal to noise].
The quality of the power supply effects the amplifier SNR, so in the
persuit of superlative oscillator phase noise, the power supply should be
as good as possible.
Resistors in the oscillator carrying DC make 1/f noise - the best in this
respect are the metal type, I think - so use metal resistors or WW.
What are the other conciderations that come into the design, for lowest
noise of the oscillator itself
Split, then
lump...;-).................................................Cheers, de : Don
ZL4GX
http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail
Virus-free.
www.avg.com
http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail
<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
On Sat, Jan 6, 2018 at 1:08 PM, Magnus Danielson <magnus@rubidium.dyndns.org
wrote:
Joseph,
On 01/05/2018 09:16 PM, Joseph Gwinn wrote:
On Fri, 05 Jan 2018 12:00:01 -0500, time-nuts-request@febo.com wrote:
Send time-nuts mailing list submissions to
If I pass both a sine wave tone and a pile of audio noise through a
perfectly
linear circuit, I get no AM or PM noise sidebands on the signal. The
only way
they combine is if the circuit is non-linear. There are a lot of ways
to model
this non-linearity. The “old school” approach is with a polynomial
function. That
dates back at least into the 1930’s. The textbooks I used learning it
in the 1970’s
were written in the 1950’s. There are many decades of papers on
this stuff.
Simple answer is that some types of non-linearity transfer AM others
transfer PM.
Some transfer both. In some cases the spectrum of the modulation is
preserved.
In some cases the spectrum is re-shaped by the modulation process. As
I recall
we spend a semester going over the basics of what does what.
These days, you have the wonders of non-linear circuit analysis. To
the degree
that your models are accurate and that the methods used work, I’m
sure it will
give you similar data compared to the “old school” stuff.
All the points about the need for linearity are correct. The best
point of access to the math of phase noise (both AM and PM) is
modulation theory - phase noise is low-index modulation of the RF
carrier signal. Given the very low modulation index, only the first
term of the approximating Bessel series is significant. The difference
between AM and PM is the relative phasing of the modulation sidebands.
Additive npose has no such phase relationship.
May I just follow up on the assumption there. The Bessel series is the
theoretical for what goes on in PM and also helps to explain one
particular error I have seen. For one oscillator with particular bad
noise, a commercial instruments gave positive PM nummbers. Rather than
measuring the power of the signal, it measured the power of the carrier.
Under the assumption of low index modulation the Bessel for the carrier
is very close to 1, so it is fairly safe assumption. However, for higher
index the carrier suppresses, and that matches that the Bessel becomes
lower. That's what happen, so a read-out of the carrier is no longer
representing the power of the signal.
However, if you do have low index modulation, you can assume the center
carrier to be as close to full power as you want, and the two
side-carriers has a very simple linear approximation.
Cheers,
Magnus
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Hi
….. except you can decide to use a “25%” design for your oscillator or you can go with a
“50%” kind of circuit. It’s going to be a bit tough finding a crystal that is 2X higher Q ….
Rick’s papers go through a bit of just why you would go with the “25%” circuit.
Bob
On Jan 6, 2018, at 9:25 AM, Magnus Danielson magnus@rubidium.dyndns.org wrote:
Hi,
I think loaded Q is being used as term these days for the effective Q of
the resonator as loaded by the support amplifier.
The Leeson model only models how noise types gets created, not how a
physical design actually works.
The modified Leeson model starts to approach the actual design.
Cheers,
Magnus
On 01/06/2018 03:19 PM, Bob kb8tq wrote:
Hi
The key point missing is the fact that any real oscillator must have a limiter
in the loop. Otherwise it will “create one” by going over the max output of this or
that amplifier. To the degree that the limiter has issues (limits poorly) you will get
AM noise.
On a practical basis, loop Q is as significant as resonator Q . The various
elements in the loop degrade the total Q by a significant amount. Getting 25 to
50% of the resonator Q is “doing well” with his or that common circuit. Yes, there
are even more layers past this ….
Bob
On Jan 6, 2018, at 1:53 AM, donald collie donaldbcollie@gmail.com wrote:
So to be lowest noise, an oscillator should have the highest Q resonator
possible in its feedback loop, operate in class "A" [for maximum
linearity], and utilise active amplifier device(s) that contribute the
least noise [both amplitude, or 1/f], and phase. This latter implies
operating the active device at maximum output level [ie signal to noise].
The quality of the power supply effects the amplifier SNR, so in the
persuit of superlative oscillator phase noise, the power supply should be
as good as possible.
Resistors in the oscillator carrying DC make 1/f noise - the best in this
respect are the metal type, I think - so use metal resistors or WW.
What are the other conciderations that come into the design, for lowest
noise of the oscillator itself
Split, then
lump...;-).................................................Cheers, de : Don
ZL4GX
http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail
Virus-free.
www.avg.com
http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail
<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
On Sat, Jan 6, 2018 at 1:08 PM, Magnus Danielson <magnus@rubidium.dyndns.org
wrote:
Joseph,
On 01/05/2018 09:16 PM, Joseph Gwinn wrote:
On Fri, 05 Jan 2018 12:00:01 -0500, time-nuts-request@febo.com wrote:
Send time-nuts mailing list submissions to
If I pass both a sine wave tone and a pile of audio noise through a
perfectly
linear circuit, I get no AM or PM noise sidebands on the signal. The
only way
they combine is if the circuit is non-linear. There are a lot of ways
to model
this non-linearity. The “old school” approach is with a polynomial
function. That
dates back at least into the 1930’s. The textbooks I used learning it
in the 1970’s
were written in the 1950’s. There are many decades of papers on
this stuff.
Simple answer is that some types of non-linearity transfer AM others
transfer PM.
Some transfer both. In some cases the spectrum of the modulation is
preserved.
In some cases the spectrum is re-shaped by the modulation process. As
I recall
we spend a semester going over the basics of what does what.
These days, you have the wonders of non-linear circuit analysis. To
the degree
that your models are accurate and that the methods used work, I’m
sure it will
give you similar data compared to the “old school” stuff.
All the points about the need for linearity are correct. The best
point of access to the math of phase noise (both AM and PM) is
modulation theory - phase noise is low-index modulation of the RF
carrier signal. Given the very low modulation index, only the first
term of the approximating Bessel series is significant. The difference
between AM and PM is the relative phasing of the modulation sidebands.
Additive npose has no such phase relationship.
May I just follow up on the assumption there. The Bessel series is the
theoretical for what goes on in PM and also helps to explain one
particular error I have seen. For one oscillator with particular bad
noise, a commercial instruments gave positive PM nummbers. Rather than
measuring the power of the signal, it measured the power of the carrier.
Under the assumption of low index modulation the Bessel for the carrier
is very close to 1, so it is fairly safe assumption. However, for higher
index the carrier suppresses, and that matches that the Bessel becomes
lower. That's what happen, so a read-out of the carrier is no longer
representing the power of the signal.
However, if you do have low index modulation, you can assume the center
carrier to be as close to full power as you want, and the two
side-carriers has a very simple linear approximation.
Cheers,
Magnus
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Moin
Disclaimer: I am by far not an expert in oscillators. Please correct me if
I am wrong.
I am putting my replies to a few mails together into one, as not to clutter
the mailinglist too much.
On Sat, 6 Jan 2018 19:53:20 +1300
donald collie donaldbcollie@gmail.com wrote:
So to be lowest noise, an oscillator should have the highest Q resonator
possible in its feedback loop, operate in class "A" [for maximum
linearity], and utilise active amplifier device(s) that contribute the
least noise [both amplitude, or 1/f], and phase.
Actually, it shouldn't. At least not if you want low phase noise.
The sensitivity of the output phase noise to the internal noise sources
changes during the period of the oscillator. AFAIK this has been first
noted by Hajimiri and Lee in [1], you can also find it mentioned in [2].
The small problem with that is, that it will lead to an increase of AM
noise, which in turn is turned into 1/f^2 and 1/f^3 PM noise through
the oscillator.
Also, you might want to back down a bit on the loaded Q, if you can
significantly improve the noise performance of the sustaining amplifier,
by better matching. (Gregory Weaver mentioned this during a discussion)
Resistors in the oscillator carrying DC make 1/f noise - the best in this
respect are the metal type, I think - so use metal resistors or WW.
The 1/f noise of resistors is lower than that of the semiconductors
involved, unless you are using carbon resistors. Hence most people
just simply ignore it. The commonly accepted theory is, that the 1/f
noise in resistors comes from the electron traps at material faults.
In carbon resistors, these are formed by the edges of the carbon particles.
In other these are formed by the way how the resistive material is deposited.
Hence thin-film and metal-foil have the lowest 1/f noise.
On Sat, 6 Jan 2018 20:12:16 -0600
Dana Whitlow k8yumdoober@gmail.com wrote:
I've long wondered if a very slow AGC might avoid the nonlinear mechanisms
issue except, of course, for things happening within the AGC loop's
bandwidth.
Is anybody reading this aware of what the truth really is?
The truth is complicated. There are so many effects that one has to
analyse and keep track that it's hard to say which one dominates in
a design, without doing extensive calculations or simulations.
At least that's my impressen, when I read papers on noise in electronics.
On Mon, 8 Jan 2018 01:02:11 +1300
donald collie donaldbcollie@gmail.com wrote:
Does any limiter, soft or hard, [and perhaps any nonlinearity of power
term 3 or greater in the amplifier of an oscillator] cause the "baseband
1/f noise to translate up to the resonator frequency [a form of
crossmodulation]?.
The upconversion happens regardless of the limiting circuit. It stems from
the sustaining amplifier being non-linear. Even running a transistor completely
in a class A configuration will lead to upconversion, because not all the noise
sources are at places where the transfer function through the transistor to the
output is linear.
I wonder this because
phase noise vs freq plots look a bit like the 1/f plots of a resistor, or
active device, or power supply.
I do not understand this question. Noise looks "the same" for all devices.
Their only difference is the relative levels of 1/f^a noise. As such, it is
hard (impossible?) to say which device causes the noise at the output of
an oscillator by just looking at its output.
Ceramic caps, and resonators [Im thinking of quartz crystals] dont pass much DC, and as I understand it, 1/f noise
is associated with dc passing through resistors, or semiconductors.
1/f noise is generally associatiated with semiconductors and (carbon)
resistors, yes. But the crystal itself has its own 1/f noise and depending
on your circuit that might be actually the limiting factor and not the
electronic circuit.
Also keep in mind that a lot of electronic components are electro-mechanical
in nature. Ie they convert mechanical noise (aka vibrations) into electrical
noise. A prime culprit of this behaviour are capacitors and inductors, but
also semiconductors are known for this.
So the
best way to go might be to have a very linear amplifier, which exhibits
very low noise [perhaps 150dB below the operating level], with an AGC loop,
that sets the operating levela little below the level at which the amp
starts to clip - this could be done with a thermistor to avoid the AGC loop
altering the [optimised] operating conditions of the amp. Alternatively you
might be able to use a tetrode device like a dual gate MOSFET, and apply
the AGC to the second gate. Thus you could keep the extremely linear amp
extremely linear. [150dB below 1Volt RMS is 0.032uV RMS].
If you google for Rohde/Poddar and noise/oscillator, you will find quite
a few papers and articles on how to build low-noise oscillators that are
only limited by the thermal noise in the 50Ω source resistance, Ie oscillators
that have a white noise floor at almost -174dBm (note: dBm not dBc).
It is "known" how to build such oscillators, but it doesn't mean it's easy :-)
Attila Kinali
[1] "A General Theory of Phase Noise in Electrical Oscillators",
Hajimiri and Lee, 1998
[2] "How Low Can They Go?", by Poddar, Rohde, Apte, 2013
http://time.kinali.ch/rohde/noise/how_low_can_they_go-2013-poddar_rohde_apte.pdf
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
Hi from Florida (it is atypical cool),ly
`
Ref 1 is really only good for an insight but to use it makes no sens and the names in ref 2 are out of order, that makes no difference.
Ulrich
In a message dated 1/8/2018 9:02:47 AM Eastern Standard Time, attila@kinali.ch writes:
Moin
Disclaimer: I am by far not an expert in oscillators. Please correct me if
I am wrong.
I am putting my replies to a few mails together into one, as not to clutter
the mailinglist too much.
On Sat, 6 Jan 2018 19:53:20 +1300
donald collie donaldbcollie@gmail.com wrote:
So to be lowest noise, an oscillator should have the highest Q resonator
possible in its feedback loop, operate in class "A" [for maximum
linearity], and utilise active amplifier device(s) that contribute the
least noise [both amplitude, or 1/f], and phase.
Actually, it shouldn't. At least not if you want low phase noise.
The sensitivity of the output phase noise to the internal noise sources
changes during the period of the oscillator. AFAIK this has been first
noted by Hajimiri and Lee in [1], you can also find it mentioned in [2].
The small problem with that is, that it will lead to an increase of AM
noise, which in turn is turned into 1/f^2 and 1/f^3 PM noise through
the oscillator.
Also, you might want to back down a bit on the loaded Q, if you can
significantly improve the noise performance of the sustaining amplifier,
by better matching. (Gregory Weaver mentioned this during a discussion)
Resistors in the oscillator carrying DC make 1/f noise - the best in this
respect are the metal type, I think - so use metal resistors or WW.
The 1/f noise of resistors is lower than that of the semiconductors
involved, unless you are using carbon resistors. Hence most people
just simply ignore it. The commonly accepted theory is, that the 1/f
noise in resistors comes from the electron traps at material faults.
In carbon resistors, these are formed by the edges of the carbon particles.
In other these are formed by the way how the resistive material is deposited.
Hence thin-film and metal-foil have the lowest 1/f noise.
On Sat, 6 Jan 2018 20:12:16 -0600
Dana Whitlow k8yumdoober@gmail.com wrote:
I've long wondered if a very slow AGC might avoid the nonlinear mechanisms
issue except, of course, for things happening within the AGC loop's
bandwidth.
Is anybody reading this aware of what the truth really is?
The truth is complicated. There are so many effects that one has to
analyse and keep track that it's hard to say which one dominates in
a design, without doing extensive calculations or simulations.
At least that's my impressen, when I read papers on noise in electronics.
On Mon, 8 Jan 2018 01:02:11 +1300
donald collie donaldbcollie@gmail.com wrote:
Does any limiter, soft or hard, [and perhaps any nonlinearity of power
term 3 or greater in the amplifier of an oscillator] cause the "baseband
1/f noise to translate up to the resonator frequency [a form of
crossmodulation]?.
The upconversion happens regardless of the limiting circuit. It stems from
the sustaining amplifier being non-linear. Even running a transistor completely
in a class A configuration will lead to upconversion, because not all the noise
sources are at places where the transfer function through the transistor to the
output is linear.
I wonder this because
phase noise vs freq plots look a bit like the 1/f plots of a resistor, or
active device, or power supply.
I do not understand this question. Noise looks "the same" for all devices.
Their only difference is the relative levels of 1/f^a noise. As such, it is
hard (impossible?) to say which device causes the noise at the output of
an oscillator by just looking at its output.
Ceramic caps, and resonators [Im thinking of quartz crystals] dont pass much DC, and as I understand it, 1/f noise
is associated with dc passing through resistors, or semiconductors.
1/f noise is generally associatiated with semiconductors and (carbon)
resistors, yes. But the crystal itself has its own 1/f noise and depending
on your circuit that might be actually the limiting factor and not the
electronic circuit.
Also keep in mind that a lot of electronic components are electro-mechanical
in nature. Ie they convert mechanical noise (aka vibrations) into electrical
noise. A prime culprit of this behaviour are capacitors and inductors, but
also semiconductors are known for this.
So the
best way to go might be to have a very linear amplifier, which exhibits
very low noise [perhaps 150dB below the operating level], with an AGC loop,
that sets the operating levela little below the level at which the amp
starts to clip - this could be done with a thermistor to avoid the AGC loop
altering the [optimised] operating conditions of the amp. Alternatively you
might be able to use a tetrode device like a dual gate MOSFET, and apply
the AGC to the second gate. Thus you could keep the extremely linear amp
extremely linear. [150dB below 1Volt RMS is 0.032uV RMS].
If you google for Rohde/Poddar and noise/oscillator, you will find quite
a few papers and articles on how to build low-noise oscillators that are
only limited by the thermal noise in the 50Ω source resistance, Ie oscillators
that have a white noise floor at almost -174dBm (note: dBm not dBc).
It is "known" how to build such oscillators, but it doesn't mean it's easy :-)
Attila Kinali
[1] "A General Theory of Phase Noise in Electrical Oscillators",
Hajimiri and Lee, 1998
[2] "How Low Can They Go?", by Poddar, Rohde, Apte, 2013
http://time.kinali.ch/rohde/noise/how_low_can_they_go-2013-poddar_rohde_apte.pdf
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.