Hybrid clock synchronization: The pull-in range of a ring network

The hybrid clock synchronization method locks subordinately to the external wide-area network while mutual locking is used within the network. This me thod has excellent reliability as a clock synchronization method for a loca l network. By using a dual-input phase lock loop (PLL), nodes that can obta in clocks externally are connected in a ring and are used as the higher lev el nodes in the proposed method. In this configuration of the synchronizati on network, other nodes are treated as lower-level nodes which obtain clock s from higher-level nodes. In this paper, the pull-in range of the synchron ization network in this configuration is obtained. First, the waveform conn ection condition within the PLL is obtained when the output frequency of th e PLL coincides with that of one of the inputs (with a smaller synchronizat ion gain). From this result, the range is derived for the output frequency to move toward the input frequency. This is considered as the operating pul l-in range. It is shown that the pull-in range of the entire ring network i s the minimum value of the dynamic pull-in range among all of the nodes. Al so, the pull-in range of the lower level nodes is considered in the state a fter convergence of the ring network. It is shown that the pull-in range be comes the minimum in the situation where the phases of the two inputs are o pposite. The above observations are confirmed by simulation. (C) 1999 Scrip ta Technica.