  This paper presents the first voltage-controlled MEMS oscillator (VCMO) based
on a Lithium Niobate (LiNbO3) lateral overtone bulk acoustic resonator (LOBAR).
The VCMO consists of a LOBAR in a closed loop with 2 amplification stages and a
varactor-embedded tunable LC tank. By adjusting the bias voltage applied to the
varactor, the tank can be tuned to change the closed-loop gain and phase
responses of the oscillator so that Barkhausen conditions are satisfied for a
particular resonance mode. The tank is designed to allow the proposed VCMO to
lock to any of the ten overtones ranging from 300 to 500 MHz. Owing to the
high-quality factors of the LiNbO3 LOBAR, the measured VCMO shows a low
close-in phase noise of -100 dBc/Hz at 1 kHz offset from a 300 MHz carrier and
a noise floor of -153 dBc/Hz while consuming 9 mW. With further optimization,
this VCMO can lead to direct radio frequency (RF) synthesis for ultra-low-power
transceivers in multi-mode Internet-of-Things (IoT) nodes.
