> Necronomicon wrote:
> > Tim Wescott wrote:
> >> Necronomicon wrote:
> >>> Tim Wescott wrote:
> >>>> Necronomicon wrote:
> >>>>> Does Eb/No, as used in digital communication
> >>>>> calculations for signal to noise ratios, take into
> >>>>> account the VCO/PLL/Reference phase noise of the carrier(s)?
> >>>>>
> >>>>> I ask because the phase noise is never really flat, and the Noise
> >>>>> Power Spectral Density, or "No", is in Watts/Hz, which is assuming
> >>>>> that the noise is flat across all frequencies (white noise).
> >>>>>
> >>>>> Certainly one could use the integrated phase noise, and just
> >>>>> add this to the integrated power of the noise floor, which would
> >>>>> be the (Watts/Hz) x (receiver noise band-width).
> >>>>>
> >>>>> But it seems like Eb/No is only considering an assumed spectrally
> >>>>> flat, white-noise, noise floor.
> >>>>>
> >>>>>
> >>>>> Thanks for any clarity on this....
> >>>>>
> >>>> Unless you have a really crappy PLL the phase noise of your carrier
> >>>> won't directly affect the decoding of your signal.
> >>>
> >>> This is incorrect. The PLL phase noise will directly
> >>> affect the bit error rate of your demodulation, especially if it's
> >>> a 16-QAM or 64-QAM signal. You'll be able to see the phase
> >>> or amplitude shift directly off a displayed constellation.
> >>>
> >>> It's less critical if it's a QPSK or BPSK, but the phase
> >>> noise
> >>> will still affect your BER.
> >>>
> >>> And my original question is if the Eb/No takes the
> >>> phase noise into account.
> >>>
> >> I reserve the right to define "crappy PLL" as one that changes the phase
> >> enough, within one bit time, to mess up the demodulation. So, by
> >> definition, I'm right :).
> >>
> >
> > When you say: "Unless you have a really crappy PLL the phase
> > noise of your carrier
> > won't directly affect the decoding of your signal"......
> >
> > ......you make it sound like phase noise is not a VCO design
> > issue
> > when this is clearly not the case, as people are constantly looking
> > for ways to increase the Q of their designs, to minimize phase noise,
> > especially
> > for 802.11a/g, with the higher OFDM data rates.
> >
> > Also, you really meant to say "within one symbol period",
> > because you can
> > have more than one bit per symbol.
> >
> Sorry if it sounded like that. I'm well aware of the interest and
> difficulty in designing low noise VCOs, and keeping them that way when
> you put them in a PLL.
>
> And yes, I should have said "one symbol period". Proofreading is good,
> it's too bad it often happens after I post...
>
You're clearly a control-systems specialist anyways, so you
have an excuse!
No worries.....
Reply by Necronomicon●October 2, 20072007-10-02
Eric Jacobsen wrote:
> On Tue, 02 Oct 2007 11:21:28 -0700, Necronomicon <radio913@aol.com>
> wrote:
>
> >Does Eb/No, as used in digital communication
> >calculations for signal to noise ratios, take into
> >account the VCO/PLL/Reference phase noise of the carrier(s)?
> >
> >I ask because the phase noise is never really flat, and the Noise
> >Power Spectral Density, or "No", is in Watts/Hz, which is assuming
> >that the noise is flat across all frequencies (white noise).
> >
> >Certainly one could use the integrated phase noise, and just
> >add this to the integrated power of the noise floor, which would
> >be the (Watts/Hz) x (receiver noise band-width).
> >
> >But it seems like Eb/No is only considering an assumed spectrally
> >flat, white-noise, noise floor.
> >
> >
> >Thanks for any clarity on this....
>
> The short answer is no. Eb/No is a power efficiency metric, used
> often to analyze the efficiencies of FEC and modulation in a
> theoretical or simulation sense. For those cases phase noise is not
> considered since it is implementation specific. So, in general Eb/No
> does not consider phase noise, nor does it consider imperfections in
> the filters or amplifiers.
>
> That doesn't mean that when you make a lab measurement to calibrate a
> system or measure performance, that phase noise doesn't affect the
> result. Clearly a measurement made on a practical system will
> include the effects of all impairments, including phase noise. Usually
> this gets lumped into an "implementation loss" term that will include
> phase noise, distortions due to filters and amplifiers, etc., etc.
>
I would expect this to be the case, as the Eb/No certainly
doesn't consider for example, the IP3s of your amplifier chains,
which would certainly be an impairment if you are in saturation
for a 64-QAM signal.
The tip-off for me is that the noise power spectral density is
in Watts/Hz, which assumes spectrally flat noise.
Ok, thanks.
BTW, your website is wonderfully unprofessional and home-grown!
Reply by Tim Wescott●October 2, 20072007-10-02
Necronomicon wrote:
> Tim Wescott wrote:
>> Necronomicon wrote:
>>> Tim Wescott wrote:
>>>> Necronomicon wrote:
>>>>> Does Eb/No, as used in digital communication
>>>>> calculations for signal to noise ratios, take into
>>>>> account the VCO/PLL/Reference phase noise of the carrier(s)?
>>>>>
>>>>> I ask because the phase noise is never really flat, and the Noise
>>>>> Power Spectral Density, or "No", is in Watts/Hz, which is assuming
>>>>> that the noise is flat across all frequencies (white noise).
>>>>>
>>>>> Certainly one could use the integrated phase noise, and just
>>>>> add this to the integrated power of the noise floor, which would
>>>>> be the (Watts/Hz) x (receiver noise band-width).
>>>>>
>>>>> But it seems like Eb/No is only considering an assumed spectrally
>>>>> flat, white-noise, noise floor.
>>>>>
>>>>>
>>>>> Thanks for any clarity on this....
>>>>>
>>>> Unless you have a really crappy PLL the phase noise of your carrier
>>>> won't directly affect the decoding of your signal.
>>>
>>> This is incorrect. The PLL phase noise will directly
>>> affect the bit error rate of your demodulation, especially if it's
>>> a 16-QAM or 64-QAM signal. You'll be able to see the phase
>>> or amplitude shift directly off a displayed constellation.
>>>
>>> It's less critical if it's a QPSK or BPSK, but the phase
>>> noise
>>> will still affect your BER.
>>>
>>> And my original question is if the Eb/No takes the
>>> phase noise into account.
>>>
>> I reserve the right to define "crappy PLL" as one that changes the phase
>> enough, within one bit time, to mess up the demodulation. So, by
>> definition, I'm right :).
>>
>
> When you say: "Unless you have a really crappy PLL the phase
> noise of your carrier
> won't directly affect the decoding of your signal"......
>
> ......you make it sound like phase noise is not a VCO design
> issue
> when this is clearly not the case, as people are constantly looking
> for ways to increase the Q of their designs, to minimize phase noise,
> especially
> for 802.11a/g, with the higher OFDM data rates.
>
> Also, you really meant to say "within one symbol period",
> because you can
> have more than one bit per symbol.
>
Sorry if it sounded like that. I'm well aware of the interest and
difficulty in designing low noise VCOs, and keeping them that way when
you put them in a PLL.
And yes, I should have said "one symbol period". Proofreading is good,
it's too bad it often happens after I post...
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html
Reply by Steve Underwood●October 2, 20072007-10-02
Tim Wescott wrote:
> Ideally your carrier is at exactly one frequency, forever.
So your ideal is for nobody to move? That would certainly help preserve
oil resources for future generations. :-)
Steve
Reply by Eric Jacobsen●October 2, 20072007-10-02
On Tue, 02 Oct 2007 11:21:28 -0700, Necronomicon <radio913@aol.com>
wrote:
>Does Eb/No, as used in digital communication
>calculations for signal to noise ratios, take into
>account the VCO/PLL/Reference phase noise of the carrier(s)?
>
>I ask because the phase noise is never really flat, and the Noise
>Power Spectral Density, or "No", is in Watts/Hz, which is assuming
>that the noise is flat across all frequencies (white noise).
>
>Certainly one could use the integrated phase noise, and just
>add this to the integrated power of the noise floor, which would
>be the (Watts/Hz) x (receiver noise band-width).
>
>But it seems like Eb/No is only considering an assumed spectrally
>flat, white-noise, noise floor.
>
>
>Thanks for any clarity on this....
The short answer is no. Eb/No is a power efficiency metric, used
often to analyze the efficiencies of FEC and modulation in a
theoretical or simulation sense. For those cases phase noise is not
considered since it is implementation specific. So, in general Eb/No
does not consider phase noise, nor does it consider imperfections in
the filters or amplifiers.
That doesn't mean that when you make a lab measurement to calibrate a
system or measure performance, that phase noise doesn't affect the
result. Clearly a measurement made on a practical system will
include the effects of all impairments, including phase noise. Usually
this gets lumped into an "implementation loss" term that will include
phase noise, distortions due to filters and amplifiers, etc., etc.
Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.ericjacobsen.org
Reply by Necronomicon●October 2, 20072007-10-02
Tim Wescott wrote:
> Necronomicon wrote:
> > Tim Wescott wrote:
> >> Necronomicon wrote:
> >>> Does Eb/No, as used in digital communication
> >>> calculations for signal to noise ratios, take into
> >>> account the VCO/PLL/Reference phase noise of the carrier(s)?
> >>>
> >>> I ask because the phase noise is never really flat, and the Noise
> >>> Power Spectral Density, or "No", is in Watts/Hz, which is assuming
> >>> that the noise is flat across all frequencies (white noise).
> >>>
> >>> Certainly one could use the integrated phase noise, and just
> >>> add this to the integrated power of the noise floor, which would
> >>> be the (Watts/Hz) x (receiver noise band-width).
> >>>
> >>> But it seems like Eb/No is only considering an assumed spectrally
> >>> flat, white-noise, noise floor.
> >>>
> >>>
> >>> Thanks for any clarity on this....
> >>>
> >> Unless you have a really crappy PLL the phase noise of your carrier
> >> won't directly affect the decoding of your signal.
> >
> >
> > This is incorrect. The PLL phase noise will directly
> > affect the bit error rate of your demodulation, especially if it's
> > a 16-QAM or 64-QAM signal. You'll be able to see the phase
> > or amplitude shift directly off a displayed constellation.
> >
> > It's less critical if it's a QPSK or BPSK, but the phase
> > noise
> > will still affect your BER.
> >
> > And my original question is if the Eb/No takes the
> > phase noise into account.
> >
> I reserve the right to define "crappy PLL" as one that changes the phase
> enough, within one bit time, to mess up the demodulation. So, by
> definition, I'm right :).
>
When you say: "Unless you have a really crappy PLL the phase
noise of your carrier
won't directly affect the decoding of your signal"......
......you make it sound like phase noise is not a VCO design
issue
when this is clearly not the case, as people are constantly looking
for ways to increase the Q of their designs, to minimize phase noise,
especially
for 802.11a/g, with the higher OFDM data rates.
Also, you really meant to say "within one symbol period",
because you can
have more than one bit per symbol.
Reply by mnentwig●October 2, 20072007-10-02
>> We'll need some serious linearity for that!
Maybe it's only my imagination, but I think I recognize your handwriting.
-mn
Reply by Tim Wescott●October 2, 20072007-10-02
Necronomicon wrote:
> Tim Wescott wrote:
>> Necronomicon wrote:
>>> Does Eb/No, as used in digital communication
>>> calculations for signal to noise ratios, take into
>>> account the VCO/PLL/Reference phase noise of the carrier(s)?
>>>
>>> I ask because the phase noise is never really flat, and the Noise
>>> Power Spectral Density, or "No", is in Watts/Hz, which is assuming
>>> that the noise is flat across all frequencies (white noise).
>>>
>>> Certainly one could use the integrated phase noise, and just
>>> add this to the integrated power of the noise floor, which would
>>> be the (Watts/Hz) x (receiver noise band-width).
>>>
>>> But it seems like Eb/No is only considering an assumed spectrally
>>> flat, white-noise, noise floor.
>>>
>>>
>>> Thanks for any clarity on this....
>>>
>> Unless you have a really crappy PLL the phase noise of your carrier
>> won't directly affect the decoding of your signal.
>
>
> This is incorrect. The PLL phase noise will directly
> affect the bit error rate of your demodulation, especially if it's
> a 16-QAM or 64-QAM signal. You'll be able to see the phase
> or amplitude shift directly off a displayed constellation.
>
> It's less critical if it's a QPSK or BPSK, but the phase
> noise
> will still affect your BER.
>
> And my original question is if the Eb/No takes the
> phase noise into account.
>
I reserve the right to define "crappy PLL" as one that changes the phase
enough, within one bit time, to mess up the demodulation. So, by
definition, I'm right :).
At any rate, I would expect that a textbook Eb/No curve doesn't take
this into account, at least if it's a basic textbook. You certainly
_could_ calculate the effect of the phase shift of the signal due to the
PLL, and probably _should_ if you expect the phase noise to be
significant. Whether an Eb/No curve that you find in a data book or a
paper takes this into account is something that you'd have to verify on
a case-by-case basis.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html
Reply by Necronomicon●October 2, 20072007-10-02
John wrote:
> On Oct 2, 3:38 pm, Tim Wescott <t...@seemywebsite.com> wrote:
> > Necronomicon wrote:
> > > Does Eb/No, as used in digital communication
> > > calculations for signal to noise ratios, take into
> > > account the VCO/PLL/Reference phase noise of the carrier(s)?
> >
> > > I ask because the phase noise is never really flat, and the Noise
> > > Power Spectral Density, or "No", is in Watts/Hz, which is assuming
> > > that the noise is flat across all frequencies (white noise).
> >
> > > Certainly one could use the integrated phase noise, and just
> > > add this to the integrated power of the noise floor, which would
> > > be the (Watts/Hz) x (receiver noise band-width).
> >
> > > But it seems like Eb/No is only considering an assumed spectrally
> > > flat, white-noise, noise floor.
> >
> > > Thanks for any clarity on this....
> >
> > Unless you have a really crappy PLL the phase noise of your carrier
> > won't directly affect the decoding of your signal. What phase noise
> > _does_ do is to raise the noise floor in the presence of nearby carriers
> > that wouldn't otherwise cause any problems.
> >
>
> But what constitutes a crappy PLL is not the same for BPSK as 256QAM,
> in other words the modulation type matters.
>
Correct! Thank you!
Last i heard, they still haven't decided on the standard for
WiMax, or 802.16, but they were considering 256-QAM.
We'll need some serious linearity for that!
Reply by Necronomicon●October 2, 20072007-10-02
Tim Wescott wrote:
> Necronomicon wrote:
> > Does Eb/No, as used in digital communication
> > calculations for signal to noise ratios, take into
> > account the VCO/PLL/Reference phase noise of the carrier(s)?
> >
> > I ask because the phase noise is never really flat, and the Noise
> > Power Spectral Density, or "No", is in Watts/Hz, which is assuming
> > that the noise is flat across all frequencies (white noise).
> >
> > Certainly one could use the integrated phase noise, and just
> > add this to the integrated power of the noise floor, which would
> > be the (Watts/Hz) x (receiver noise band-width).
> >
> > But it seems like Eb/No is only considering an assumed spectrally
> > flat, white-noise, noise floor.
> >
> >
> > Thanks for any clarity on this....
> >
> Unless you have a really crappy PLL the phase noise of your carrier
> won't directly affect the decoding of your signal.
This is incorrect. The PLL phase noise will directly
affect the bit error rate of your demodulation, especially if it's
a 16-QAM or 64-QAM signal. You'll be able to see the phase
or amplitude shift directly off a displayed constellation.
It's less critical if it's a QPSK or BPSK, but the phase
noise
will still affect your BER.
And my original question is if the Eb/No takes the
phase noise into account.