klokdiscipline

Klokdiscipline, or clock discipline, is a control technique used to keep a local clock in synchrony with a reference time source. The aim is to minimize phase offset and frequency drift between the local oscillator and the reference, yielding stable and accurate timekeeping for systems that rely on precise timing.

How it works: A reference clock provides a stable signal. A phase detector compares the phase of the local clock to the reference, producing an error signal. A loop filter shapes this error, and a controller adjusts the local oscillator to reduce the error. The loop is typically a phase-locked loop that controls a voltage- or digitally-controlled oscillator, which in turn drives a stable oscillator such as an OCXO or TCXO.

Common applications: telecommunications infrastructure, data centers, financial networks, and test equipment requiring precise timing. GPS-disciplined oscillators (GPSDOs) use GPS time as the reference, while networks use NTP or IEEE 1588 Precision Time Protocol to synchronize multiple devices with a disciplined clock.

Variants and performance: holdover mode preserves time when the reference link is lost. Performance is described by phase noise, time error, and frequency stability (Allan deviation). Trade-offs include lock time, level of jitter, power consumption, and temperature sensitivity.

Related concepts include phase-locked loop, holdover, Allan deviation, GPS time, NTP, and IEEE 1588 PTP.