[ntp:questions] Kernel PLL, microkernel and the simulator.

blu brian.utterback at gmail.com
Wed Jul 23 01:43:37 UTC 2008


On Jul 21, 10:35 pm, "David L. Mills" <mi... at udel.edu> wrote:
> Brian,
>
> The data actually used to update the clock can be as old as seven poll
> periods old. This is the result of the clock filter and is expected.
> However, the dynamics of the clock discipline, in particular the time
> constant, are designed for this condition. Theory requires that the
> sampling rate of the feedback loop be at least the Nyquist rate, which
> is twice the bandwidth (inverse time constant) of the loop filter. In
> particular, the sampling rate of the NTP loop, even using only every
> seventh sample, is twice the Nyquist rate.
>
> Dave
>

Okay, so how is the bandwidth equal to the inverse TC, and is that the
TC as in 3 or as in 2^3=7? I don't understand the meaning of the term
bandwidth in this context. And when you say that it works even if you
only use every seventh sample, is that even if the sample is seven
poll intervals old every time?

Brian Utterback
brian dot utterback at sun dot com




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