On Jan 23, 10:41�pm, "Grant" <nos...@nospam.com> wrote:
> The application requires the phase of an input audio sinusoid be measured
> accurately. �Specifically I need to measure when the tone's zero crossing
> occurs within about 0.1 degree.
>
> Grant
>
>
> The application requires the phase of an input audio sinusoid be measured
> accurately. Specifically I need to measure when the tone's zero crossing
> occurs within about 0.1 degree.
within .1 degree of what reference? or do you mean "to within .1
degree"? How do you measure degrees? If 180 degrees is represented by 12
useful bits, then the best you can hope for is .044 degrees.
Jerry
--
Engineering is the art of making what you want from things you can get.
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Reply by Jerry Avins●January 24, 20082008-01-24
Grant wrote:
> Yes, I understand. But what I'm asking is how small can "made to approach
> zero" be in practice?
>
> It's an analog VCO implemented in DSP. Is 0.1 degree reasonable in practice
> given very high S/N and long acquisition time? To me that seems amazingly
> good resolution but I have no experience to base that feeling on.
Part of the answer depends on the digital resolution. However you
measure frequency, you can't get closer than one bit.
Jerry
--
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
Reply by Grant●January 23, 20082008-01-23
The application requires the phase of an input audio sinusoid be measured
accurately. Specifically I need to measure when the tone's zero crossing
occurs within about 0.1 degree.
Grant
"Mark" <makolber@yahoo.com> wrote in message
news:51784ea2-0bac-49c6-893b-a9a64b35f70d@e10g2000prf.googlegroups.com...
>
> It's an analog VCO implemented in DSP. Is 0.1 degree reasonable in
> practice
> given very high S/N and long acquisition time? To me that seems amazingly
> good resolution but I have no experience to base that feeling on.
>
> Grant
>
I don't know what an analog VCO implemented in DSP means.
If it is a real analog PLL the phase error can approach zero as the DC
loop gain is increased (i.e. the loop contains an integrator) and
subject to any DC offset or other errors.
I suspect I still don't understand your question. What does resolution
mean to you in this context?
Mark
Reply by Mark●January 23, 20082008-01-23
>
> It's an analog VCO implemented in DSP. �Is 0.1 degree reasonable in practice
> given very high S/N and long acquisition time? �To me that seems amazingly
> good resolution but I have no experience to base that feeling on.
>
> Grant
>
I don't know what an analog VCO implemented in DSP means.
If it is a real analog PLL the phase error can approach zero as the DC
loop gain is increased (i.e. the loop contains an integrator) and
subject to any DC offset or other errors.
I suspect I still don't understand your question. What does resolution
mean to you in this context?
Mark
Reply by Grant●January 23, 20082008-01-23
Yes, I understand. But what I'm asking is how small can "made to approach
zero" be in practice?
It's an analog VCO implemented in DSP. Is 0.1 degree reasonable in practice
given very high S/N and long acquisition time? To me that seems amazingly
good resolution but I have no experience to base that feeling on.
Grant
"Mark" <makolber@yahoo.com> wrote in message
news:0dacf57c-7ab0-49fb-ad59-23103b704782@d21g2000prf.googlegroups.com...
On Jan 22, 1:20 pm, "Grant" <nos...@nospam.com> wrote:
> Is there a limit to achievable resolution of a phase-locked loop given no
> noise and arbitrary acquisition time? If so, what is that limit?
>
> For example, is 0.1 degree phase resolution of a 10 kHz sinusoid
> reasonably
> achievable in practice if we assume >60 dB S/N, no frequency error and
> tens
> of seconds to acquire?
>
> Thanks.
I don't understand your question.
An analog VCO has infinite resolution, and in a PLL it can lock
exactly to any frequency and any phase (in it's range). The phase
error when locked depends on implementation details but can be made to
approach zero.
Are you using an analog VCO or a DDS based VCO?
Mark
Reply by Mark●January 23, 20082008-01-23
On Jan 22, 1:20�pm, "Grant" <nos...@nospam.com> wrote:
> Is there a limit to achievable resolution of a phase-locked loop given no
> noise and arbitrary acquisition time? �If so, what is that limit?
>
> For example, is 0.1 degree phase resolution of a 10 kHz sinusoid reasonably
> achievable in practice if we assume >60 dB S/N, no frequency error and tens
> of seconds to acquire?
>
> Thanks.
I don't understand your question.
An analog VCO has infinite resolution, and in a PLL it can lock
exactly to any frequency and any phase (in it's range). The phase
error when locked depends on implementation details but can be made to
approach zero.
Are you using an analog VCO or a DDS based VCO?
Mark
Reply by HardySpicer●January 23, 20082008-01-23
On Jan 23, 7:20 am, "Grant" <nos...@nospam.com> wrote:
> Is there a limit to achievable resolution of a phase-locked loop given no
> noise and arbitrary acquisition time? If so, what is that limit?
>
> For example, is 0.1 degree phase resolution of a 10 kHz sinusoid reasonably
> achievable in practice if we assume >60 dB S/N, no frequency error and tens
> of seconds to acquire?
>
> Thanks.
All depends on t he dynamics of your loop. You need to maintain
stability whilst having a massive gain at low frequencies. The
ultimate would be to have a pure integrator + phase-lead as a filter.
The transfer function will then be
K/s^2(1+sT1)/(1+sT2)...T1=10T2 (say).
You will also need a maximum bandwidth possible which is a function of
the 2fcarrier feedthrough term (how much can you stand). It's all
servo stuff really.
Hardy
Reply by John●January 22, 20082008-01-22
On Jan 22, 1:20�pm, "Grant" <nos...@nospam.com> wrote:
> Is there a limit to achievable resolution of a phase-locked loop given no
> noise and arbitrary acquisition time? �If so, what is that limit?
>
> For example, is 0.1 degree phase resolution of a 10 kHz sinusoid reasonably
> achievable in practice if we assume >60 dB S/N, no frequency error and tens
> of seconds to acquire?
>
> Thanks.
There was an interesting article in IEEE Trans Comm a while back by
Floyd Gardner, called "Frequency Granularity in Phase Locked Loops".
You might have a look.
John
Reply by Grant●January 22, 20082008-01-22
Is there a limit to achievable resolution of a phase-locked loop given no
noise and arbitrary acquisition time? If so, what is that limit?
For example, is 0.1 degree phase resolution of a 10 kHz sinusoid reasonably
achievable in practice if we assume >60 dB S/N, no frequency error and tens
of seconds to acquire?
Thanks.