A 300-500 MHz Tunable Oscillator Exploiting Ten Overtones in Single Lithium Niobate Resonator

TL;DR

This paper introduces a voltage-controlled MEMS oscillator based on Lithium Niobate resonators that can tune across ten overtones from 300 to 500 MHz, achieving low phase noise and low power consumption for IoT applications.

Contribution

It presents the first VCMO utilizing a Lithium Niobate LOBAR with tunable overtones, enabling multi-frequency operation with high quality factor and low phase noise.

Findings

Achieved low phase noise of -100 dBc/Hz at 1 kHz offset

Demonstrated tuning across ten overtones from 300 to 500 MHz

Power consumption of only 9 mW

Abstract

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.