Synchronous detection of dual signals based on constant-drive technique of weakly coupled resonators

The demand for highly sensitive and accurate sensors has grown significantly, particularly in the field of Micro-Electro-Mechanical Systems technology. Mode-localized sensors based on weakly coupled resonators have garnered attention for their high sensitivity through amplitude ratio outputs. However, when measuring multiple signals by weakly coupled resonators, different signals can interfere with each other, causing high cross-sensitivity. This cross-sensitivity greatly complicates signal separation and makes accurate measurement extremely difficult, impacting system performance. To address this issue, the study proposes an innovative constant-drive technique of weakly coupled resonators. This technique significantly reduces crosstalk between signals while maintaining high sensitivity of amplitude ratio output. The method is theoretically validated by analyzing amplitude ratios under signal perturbations in non-damped conditions, demonstrating perfect elimination of cross-interference. Finite element analysis under damping conditions further validated the constant-drive technique, showing a cross-sensitivity of 0.054%, nearly three orders of magnitude lower than that of mode-localized sensors. Experimental validation confirmed the effectiveness of the proposed technique, with the cross-sensitivity of the mode-localized method measured at 26.3% and 28.7%, respectively, while the constant-frequency drive achieved significantly lower values of 3.1% and 1.1%. This demonstrates a successful reduction in cross-sensitivity by an order of magnitude, meeting the performance requirements for typical MEMS biaxial sensor applications. This method is highly significant for mode-localized sensors, offering potential for developing multi-signal measurement devices like multi-axis accelerometers, force sensor, electric field sensor and mass sensor.