76.8 MHz, 105 ppm temperature stable, 106 fs jitter AlN-on-Si MEMS oscillator for cellular applications

This paper accounts on the design of a low phase noise 76.8 MHz AlN-on-silicon reference oscillator using SiO₂ for passive temperature compensation. The work targets LTE cellular applications. This study demonstrates thorough theoretical optimizations of all the crucial parameters for AlN-on-silicon width extensional mode resonators, filling into the knowledge gap which targets tens of megahertz frequency range for this type of resonators. Series resonance oscillator achieves phase noise of -127 dBc/Hz at 1 kHz, and -161 dBc/Hz at 1MHz offset. The oscillator consumes 850μA using 1.8V supply in 65nm CMOS, with integrated root mean square jitter of 106 fs (10 kHz-20 MHz), figure-of-merit of 216 dB and a startup time of 250μs. The paper presents a platform for high performance MEMS reference oscillators; where, it proves the applicability of replacing bulky quartz with MEMS resonators in wireless handsets, hence reducing cost and area.