Abstract
This paper introduces a new type of multi-degree-of-freedom cascaded hybrid electro-mechanical resonator system with ultra-high sensitivity, enhanced measurement range, and high signal-to-noise ratio, which can be used for many diverse applications. The structure is introduced in detail, and a full theoretical analysis of its performance in terms of sensitivity, noise floor, and measurement range is provided. To validate the theoretical analysis, FPGA implementations of 3- and 5-DoF prototype systems are verified with a QCM resonator and a DETF resonator to detect both mass and stiffness change, showing a high consistency between measurement results and theoretical calculations. By cascading multiple digital IIR resonators with a mechanical resonator and applying small coupling factors (1/1024 for the 3-DoF system and 1/64 for the 5-DoF system) in the digital domain, the normalized sensitivity of the proposed system is 10 times higher than the state-of-the-art weakly-coupled resonator systems. The measurement results confirm that the proposed system achieves an ultra-high normalized sensitivity of about 524000 (3-DoF) and 3145000 (5-DoF), respectively. Due to the high compatibility with different types of mechanical resonators and its high tunability, the proposed system has the potential to be a general solution towards applications requiring ultra-high sensitivity. And because of its cascaded structure, the proposed system can also be implemented as a closed-loop system, like a single mechanical resonator does.