Super-high-frequency-band injection-locked two-divider oscillator using thin-film bulk acoustic resonator

An injection-locked divider oscillator that converts a 6-GHz-band signal into a 3-GHz-band signal was developed. The injection-locked divider oscillator was specifically designed to lock on the clock transition frequency of Rb-87 of 6.824 GHz to provide a laser modulation signal at 3.417 GHz for an on-chip coherent population trapping atomic clock system. To obtain high frequency stability and low-phase noise with low power consumption in the super-high-frequency band, a thin-film bulk acoustic resonator is used instead of the conventional LC tank circuit. The fabricated oscillator operated well with a power consumption of 4.5 nW. The maximum lock range was 1.5% in fractional frequency. Also, unlike the conventional injection-locked divider oscillator with an LC tank, the bifurcation of the lock range width was observed when sweeping the injection power of the 6-GHz-band signal, and in the down sweep, the locking operation was maintained even at an injection power of -20 dBm.