Microwave reflectometry: A high-resolution technique for measuring vibration of capacitive microresonators

Abstract

The paper proposes a novel technique for measuring the vibration of capacitive micro-electromechanical resonators. Based on microwave reflectometry in the gigahertz range, the technique offers signal-to-noise ratio greater than 100 dB for the studied device and it rejects any parasitic crosstalk due to stray capacitances. Experiments demonstrate that amplitude resolution better than 10 fm/√Hz is achieved, which competes with standard optical interferometry. The technique is particularly appropriate for electrical characterization of MEMS devices but also for signal processing of resonant sensors when large-bandwidth, high signal-to-noise ratio and fully electrical detection is required.

When capacitive transduction meets the thermomechanical limit: Towards femto-newton force sensors at very high frequency

“…Capacitive sensing is easily integrated in MEMS devices but the low efficiency and parasitic crosstalk at high frequencies are detrimental to SNR and SBR. Recent advances in detection using microwaves have shown that the capacitive transduction can achieve exquisite displacement resolution and compete with optical methods [8]. Here we show that it makes possible to measure the thermomechanical vibration of high-stiffness resonators, paving the way for ultimate sensitivities.…”