UHF piezoelectric quartz mems magnetometers based on acoustic coupling of flexural and thickness shear modes

Abstract

This paper reports the design, fabrication, and characterization of piezoelectric quartz MEMS magnetometers based on acoustic coupling between resonance modes. The magnetic sensors described herein employ a novel transduction scheme to upconvert the desired near-DC magnetic field signal (using the fundamental flexural mode) onto frequency modulated (FM) sidebands of the primary quartz thickness shear (TS) oscillation at frequencies above 500 MHz. First-generation devices exhibit flexural and TS resonances at 2.77 kHz and at 583.31 MHz, respectively, and magnetic sensitivity of 63.6 V/T was measured with an AC loop current of 9.2 mA. This novel sensing method, intended for electronic compassing, illuminates the interactions between low and high frequency acoustic modes within resonant devices.