Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
DESY, Hamburg, Germany
The phase reference signal reliability is of utmost importance for continuous operation of the European XFEL machine. Since even very short interruption or glitch in the reference signal might break the precise synchronisation between subsystems, it is desirable to minimize probability of such events. While master oscillators often have a hot-spare to speed-up recovery after a failure, whether switched manually or electronically, it does not save from time-consuming resynchronisation. Our experience from testing and commissioning E-XFEL 1.3 GHz Master Oscillator (MO) shows that a struggle to achieve demanding phase-noise requirements might negatively impact reliability of the system. In this paper we present an approach which allows for quick switching between independent reference generation channels while maintaining continuity of the output signal. This is a first step towards autonomous redundancy solution for the E-XFEL MO which will maintain continuous reference signal even in case of a failure of one of the generation channels.
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
DESY, Hamburg, Germany
The Master Oscillator system of the European XFEL was built using frequency synthesis techniques that were found to have the best phase noise performance. This includes low noise frequency multipliers and nonÂmultiplying phase lock loops, incorporated in the system to shape its output phase noise spectrum. Jitter of the output signal strongly depends on phase noise transmittance of the PLL and suboptimal design can worsen it by orders of magnitude. Taking into consideration that the PLL open loop transmittance usually can be shaped in multiple ways, and that the accurate phase noise measurements can easily take more than 30 minutes, designing an automated tool becomes a necessity. For this purpose an approach to the tuning system construction was chosen in order to make the phase noise optimisation process simpler. This paper describes the optimisation of PLL synthesizer phase noise, done to improve the performance of the European XFEL MO. We present the phase noise optimisation process and achieved results.