Improved clock synchronization accuracy through optimized servo parametrization

Slave servo clocks are of essential importance to maintain synchronization between the grandmaster and its associated slaves. The servo structure and parametrization should ideally achieve fast settling times, minimize the clock jitter, and keep the clock offset below a predefined boundary. Commonly used solutions for this challenge are adder-based clocks or voltage controlled oscillators together with proportional-integral (PI) controllers. This paper shows how to capture and calculate the impairments relevant for the servo clocks, in particular the oscillator wander. Based on these data we show that proper parametrization of the PI controller is the key for minimizing the clock offset to the grandmaster.