Drift-free FBAR oscillator using an atomic-resonance-stabilization technique

We developed a thin-film bulk acoustic resonator oscillator (FBAR-OSC) with drift-free and excellent frequency stability. The FBAR-OSC outputted the 3.5 GHz band oscillation and successfully stabilized it employing the coherent population trapping (CPT) resonance of clock transition in Rb alkali metal atoms. As a result of the stabilization, the temperature drift was canceled, and the frequency fluctuation was suppressed to 0.5 ppb or less in the measurement time of 104 s.