Users manual
NR2110-OG
Revision #:
J
Date:
3/17/17
Page #:
31 of 46
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Typical Phase Noise Performance-Rubidium with OCXO
When the stability of an atomic or crystal source is not sufficient a GNSS disciplined
source is an option. A GNSS receiver is installed and timing information from the GNSS
is used to discipline the timing device. Timing accuracy to a few ppb is readily
achievable.
The GNSS is used to provide timing for a DDS (direct digital waveform synthesizer).
While the DDS has outstanding long-term accuracy, the short-term stability very poor
due to the nature of the timing source. A GNSS timing source has considerable short-
term instability due to the numerous radio effects-multi-path, signal weakness etc. In
order to develop a stable reference, the GNSS timing waveform is used to discipline a
low noise source with a Kalman filter. A good example of the improved jitter
performance of a Kalman filter is shown below:
