The challenge

Background and context

Clocks based on atomic transitions in the microwave regime, also known as atomic clocks, are among the most developed quantum sensors. These atomic clocks paved the way for Global Navigation Satellite System (GNSS) and GPS.

GPS denial remains one of the largest defense timing problems in modern conflicts. GPS can be naturally unavailable such as in subterranean indoor facilities and underwater, or when the access to GPS is forcefully denied by means of GPS’ signal blocking/overriding/altering. A widespread, precise, and compact timing solution is essential in domains including navigation, communications, electronic warfare (EW), as well as intelligence, surveillance, and reconnaissance (ISR). Currently, defence timing is reliant on the distribution of GPS signals, which synchronizes local clocks to maintain timing between GPS updates.

More recently, clocks based on atomic transitions in the optical regime, also known as quantum clocks, are being developed and investigated for PNT application. Quantum clocks have demonstrated timing errors well below 1 nanosecond (ns) per day. However, these clocks are not tactical grade. A tactical-grade clock is identified as follows:

• enhanced precision;
• reliability;
• durability;
• ruggedness.

These attributes make tactical grade clocks suitable for military applications such as, but not limited to EW, ISR, Secure Communications. This advancement would facilitate reliable signal assurance, extensive communication security, and the realization of high-bandwidth communications (HBC).

Essential outcomes

We are seeking innovative solutions for tactical-grade clocks with the capability to sustain microsecond (μs) precision over 24 hours which would alleviate the dependency on GPS-based timing for several defence operations.

Proposed solutions must:

• Have an operating range of at least -40 to +85°C;
• Have a temperature stability over operating range of at least ±5 parts per billion (ppb);
• Ensure that the time error does not exceed 1 μs over a 24-hour period;
• Have vibration sensitivity below 0.3 ppb/g from 10 Hz to 10 kHz; and,
• Be able to survive 30,000 g shock.

Desired outcomes

Proposed solutions should include capabilities and considerations such as, but not limited to, the following:

• Offer a ‘plug-and-play’ solution that is interoperable with existing systems.
• Offer package with a weight <20 g and volume <1,000 mm³.
• Have steady state power consumption below 300 mW.
• Be able to survive a minimum of 70 g vibrations.
• Be suitable for radar applications with low phase-noise, with an Allan deviation of 10^-10 in 1s.