The Rubidium-Crystal Oscillator Hybrid Development Program

The rubidium-crystal oscillator hybrid (RbXO) will make precise time available to systems that lack the power required by atomic frequency standards. The RbXO consists of two subassemblies in separate enclosures. One contains a small rubidium frequency standard (RFS) without its internal oven-controlled crystal oscillator (OCXO), plus interface circuits. The second contains a low-power OCXO, and additional interface circuits. The OCXO is on continuously. Periodically, e.g., once a week, the user system applies power to the RFS. After the few necessary for the warmup of the RFS, the interface circuits adjust the frequency of the OCXO to the RFS reference, then shut off the RFS. The OCXO enclosure is separable from the RFS enclosure so that manpacks will be able to operate with minimum size, weight, and power consumption, while having the accuracy of the RFS for the duration of a mission. A prototype RbXO's RFS has operated successfully for 4200 on-off cycles. Parallel efforts on a Phase 2 RbXO development are in progress. Two sources for the RbXO are scheduled to be available during 1986.