Mutual Synchronization with 24 GHz Oscillators

This work presents synchronization of two bidirectionally delay-coupled phase locked loop (PLL) systems with voltage controlled oscillator frequencies of 24 GHz to validate a non-hierarchical clock distribution approach. For this purpose, a PLL architecture that allows mutual coupling between two such nodes is introduced. An existing phase domain model is extended to include the nonlinear response of the oscillator to the tuning signal. With this extension the frequencies and phase-relations of self-organized synchronized states can be precisely predicted. This is verified by measurements obtained from two synchronized PLLs for different time delays and division factors. The predictions of the model are in good agreement with the measurements. For time delays up to 14 ns it is shown that self-organized synchronization is feasible at microwave frequencies.