A study of interference in synchronous systems

The influence of interference and coupling in synchronous systems is investigated. Our new approach based on the linear time-variant model in oscillatory systems lends new insight into interference and coupling phenomena in synchronous systems. According to the analysis, it is possible that a small perturbation to an oscillator is enhanced by positive feedback through coupling with another oscillatory system. This implies that the inherent phase error caused by thermal noise can lead to a large amount of jitter by interference even in the absence of external noise. The analysis also reveals the relationship between the jitter occurrence and frequency difference in a plesiochronous system. Additionally, it is shown that the coupling within a closed-loop system can limit the bandwidth of a phase-locked loop and cause the peak gain of the response of the phase error. We confirmed these analytical results by measurements conducted on test chips