Novus NR300, Руководство пользователя

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USERS MANUAL NR300
REVISION D
DATE 8/16/21
Page #: 10 of 48 www.novuspower.com
Rubidium Clock
The Rubidium reference employs a coherent trapping (CPT) technique to
interrogate an atomic frequency. A laser illuminates atoms in a resonant cell with
polarized radiation. The laser excitation significantly reduced Rb power
consumption compared to a conventional Rb source plasma cell. A microwave
synthesizer provides the energy for the two sub-bands. Light passing through the
resonant cell is modulated at resonance and the intensity of the light
transmissibility is used to control the microwave frequency. Locked to the atomic
frequency, the microwave frequency is the basis for the 10 MHz generated. The
stability of the source is less than 1 ppb/year which is almost two orders of
magnitude better than a typical OCXO. It is successfully used in applications
where long-term stability is a necessity, but GNSS may not be accessible.
During GNSS lock, the Rb atomic clock output frequency of 10 MHz is
synchronized to the GNSS PPS. The 10 MHz clock drives a counter to generate
a PPS signal. That counter is initially synchronized to the GNSS PPS to within
200 ns. During the discipline period, the Rubidium generated PPS will then
follow the GNSS PPS until “Discipline Good” status is achieved. During this
discipline period, the Rubidium status will show “Discipline Wait” while the
Rubidium source adjusts its frequency output.
Once the full synchronization and discipline has taken place, the PPS accuracy is
dictated by the atomic clock.