In collaboration with Tohoku University and Tokyo Institute of Technology, Senior Researcher Motoyo Hara of the National Institute of Information and Communications Technology (NICT) has succeeded in developing a simple compact atomic clock system that does not require the conventional complicated frequency multiplication process.
In order to build a highly accurate and uniform synchronization network, it is important not only to improve the accuracy of atomic clocks, but also to expand communication devices equipped with atomic clocks.However, atomic clocks are not portable in terms of size, weight, and power consumption, so they are limited to mounting on a small number of GPS satellites and radio base stations.In Europe and the United States, research is being conducted on the miniaturization of atomic clocks, but it is still huge, with a size of several centimeters square, to be mounted on terminals such as smartphones.
This time, the research team focused on "thickness longitudinal vibration of piezoelectric thin film" that can obtain good resonance in the GHz band for the miniaturization of atomic clocks.By utilizing this vibration, we succeeded in developing a simple microwave oscillator that does not require a crystal oscillator and a frequency multiplication circuit.As a result, the atomic clock system can be significantly reduced in size and power consumption, and the chip area can be reduced by about 30% and the power consumption can be reduced by about 50% when compared with commercially available small atomic clocks. ..
In addition, in order to tackle the issues of miniaturization and mass productivity when acquiring resonance from alkali metal elements, we have independently developed a small rubidium gas cell that can be manufactured by the wafer process.When this small gas cell was tuned (atomic clock operation) in combination with the previous microwave oscillator, frequency stability of 1 to the -10th power was obtained in 11 second.This is an improvement in performance by an order of magnitude or more compared to a commercially available small atomic clock, and it can be said that it shows excellent stability.
If the technology developed this time is put into practical use, it will be possible to mount atomic clocks, which are frequency and time standards that have been limited to artificial satellites and base stations, on general-purpose communication terminals such as smartphones. Not only that, it is expected to create new markets such as robot control (indoor drones and diving systems).
The content of this report was presented at "The 31st IEEE International Conference on Micro Electro Mechanical Systems (MEMS 2018)", the world's largest international conference on microelectromechanical systems (MEMS).