  The paper investigates the synchronization of a network of identical linear
state-space models under a possibly time-varying and directed interconnection
structure. The main result is the construction of a dynamic output feedback
coupling that achieves synchronization if the decoupled systems have no
exponentially unstable mode and if the communication graph is uniformly
connected. The result can be interpreted as a generalization of classical
consensus algorithms. Stronger conditions are shown to be sufficient but to
some extent, also necessary to ensure synchronization with the diffusive static
output coupling often considered in the literature.
