3 ms·
If I read correctly: GNSS PPS is more jittery but does not drift. The MAC has 1000x less jitter but drifts. You can cleverly combine them with statistics and m
by hoseja 5y ago
If I read correctly:
GNSS PPS is more jittery but does not drift. The MAC has 1000x less jitter but drifts. You can cleverly combine them with statistics and magic to get the best of both worlds.
- mananaysiempre 5y agoFrom what I remember of textbook discussions of atomic clocks, stabilizing drifting oscillators is also in part how normal, old (50+ years) atomic clocks work as well, isn’t it? You have a fiddly and unreasonably high-frequency reference, you slave a relatively garden-variety standard like an environmentally controlled piezoelectric crystal to it, and then feed your periodic signals, counters, etc. off that.
- willis936 5y agoYes. Surprisingly, atomic clocks have high jitter compared to ovenized quartz oscillators. Every atomic clock package is outputting its signal from a quartz oscillator that is disciplined by the atomic oscillator.
- willis936 5y agoPhase-locked loops[0] are not magic ;) Also I imagine they are using a bog standard Kalman filter[1]. 0. https://en.wikipedia.org/wiki/Phase-locked_loop https://en.wikipedia.org/wiki/Phase-locked_loop 1. https://en.wikipedia.org/wiki/Kalman_filter https://en.wikipedia.org/wiki/Kalman_filter
- Unklejoe 5y agoI've implemented this (using GPS PPS to discipline a clock) using regular old PI control loops. I just make the loop damped enough to filter out the GPS PPS jitter and you're good.