Clock Monitoring and Control Unit
The CMCU is a high-performance 10.23 MHz master clock generation unit for satellite navigation systems. Two frequency synthesizers can select independently between two input 9.99 to 10.01 MHz Atomic Clock frequency references as a basis for the master clock generation. One of the two synthesizer outputs is selected to provide the master clock for the payload and is distributed to up to four identical outputs. The output signal of the second synthesizer provides a hot redundant alternative for the master clock with seamless switching (no distortion of the output signal). A phase meter monitors the output phase of the active synthesizer against the hot redundant one.
Maximum reliability is achieved through a design without microcontroller. The TM TC interface is implemented as hard wired logic and can be addressed by serial and high-level commands. A phase synchronous output switching between active and redundant synthesizer is available. Optional features like parameter-based clock drift compensation or synthesizer adaptation to source characteristics can be implemented.
The CMCU can be operated with rubidium, passive hydrogen maser and caesium clocks to form a complete timing subsystem. The CMCU in the Galileo configuration operates with passive hydrogen maser and rubidium clocks