Microwave oscillator using piezoelectric thin-film resonator aiming for ultraminiaturization of atomic clock

• Published in: Review of scientific instruments Vol. 89; no. 10; pp. 105002 - 105008
• Main Authors: Hara, M., Yano, Y., Kajita, M., Nishino, H., Ibata, Y., Toda, M., Hara, S., Kasamatsu, A., Ito, H., Ono, T., Ido, T.
• Format: Journal Article
• Language: English
• Published: United States 01.10.2018
• ISSN: 0034-6748; 1089-7623
• DOI: 10.1063/1.5048633

We developed a microwave oscillator and a micro electromechanical systems-based rubidium cell for the miniaturization of atomic clocks. A thin-film bulk acoustic resonator (FBAR) having a resonant frequency of the fundamental mode in the 3.5 GHz band was employed instead of a crystal resonator. It delivers a clock transition frequency of Rb atoms of 3.417 GHz without the need for a complicated frequency multiplication using a phase-locked loop. This topology considerably reduces the system scale and power consumption. For downsizing the atomic clock system toward the chip level as well as mass production, a microfabricated gas cell containing Rb and N2 gases was also developed. These microcomponents were incorporated into an atomic clock test bench, resulting in a clock operation with a short-term frequency instability of 2.1 × 10−11 at 1 s. To the best of our knowledge, this is the first report of a coherent population trapping clock operation using an FBAR-based microwave oscillator as well as a microfabricated gas cell.