Hybrid clock synchronization: Condition for the existence of steady state in a ring network
Haruki Yahata · Electronics and Communications in Japan (Part I Communications) · 1996
Abstract In the clock synchronization of the closed area network (such as local area network (LAN) and metropolitan area network (MAN)) to the wide area network, it is advantageous to use the hybrid synchronization from the viewpoint of reliability, where the master‐slave synchronization is applied at several points from the wide area network, and the mutual synchronization is applied within the closed area network. This paper considers the case where the hybrid synchronization is applied to the ring‐type area network and derives the condition for the existence of the stable phase state. When the synchronization circuit is a two‐input complete integrating second‐order PLL with the sinusoidal or equilateral triangular phase comparator characteristic, the sufficient condition for the existence of the stable phase state of the whole network is that the ratio of the gain for the mutual synchronization to the gain for the master‐slave synchronization is less than 1 in at least one PLL. When the synchronization circuit is the incomplete integrating PLL, the sufficient condition is that the above gain ratio is less than a certain limit in at least one PLL, and the ratio is above the inverse of that limit in other PLL, where the limit is less than 1 and is determined by the difference between the input frequency from the wide area network and the center frequency of PLL as well as the magnitude of the gain. The above properties are shown theoretically and are verified also by computer simulation.