Space time clock: An on-chip clock with 10⁻¹² instability

High precision and stable clock is extremely important in communication and navigation. The miniaturization of the clocks is considered to be the trend to satisfy the demand for 5G and the next generation communications. Based on the concept of meter bar and the principle of the constancy of light velocity, we designed a micro clock, Space Time Clock (STC), with the size smaller than 1 mm × 1 mm and the power dissipation less than 2 mW. Designed in integrated circuit of 0.18 μm technology, the instability of STC is assessed to be 2.23 × 10⁻¹² and the trend of the instability is reversely proportional to τ. With the potential ability to reach the level of 10⁻¹⁶ instability on chip in the future, the period of the STC’s signal is locked on the delay time defined by the meter bar which keeps the time reference constant. Because of its superior performance, the STC is more suitable for mobile communication, PNT (Positioning, Navigation and Timing), embedded processor and deep space application, and becomes the main payload of the ASRTU satellite scheduled to launch next year and investigate in space environment.