A Sub-1 Hz Resonance Frequency Resonator Enabled by Multi-Step Tuning for Micro-Seismometer

Area of Science:

• Seismology
• Micro-electro-mechanical systems (MEMS)
• Sensor technology

Background:

• Traditional seismometers often struggle with achieving ultra-low resonance frequencies required for detecting subtle seismic activities.
• Electrical tuning of micro-electro-mechanical system (MEMS) resonators near zero spring constant presents significant challenges due to diverging frequency shifts.

Purpose of the Study:

• To propose and validate a sub-1 Hz resonance frequency MEMS resonator suitable for seismometer applications.
• To address the challenges of electrical fine-tuning at near-zero spring constants in MEMS resonators.
• To enhance the shock robustness and dynamic range of low-frequency MEMS resonators.

Main Methods:

• An ultra-small spring constant MEMS resonator design was developed.
• A multi-step electrical tuning method was proposed to overcome tuning difficulties at near-zero spring constants.
• A force-balanced method was employed to null mass displacement using feedback force.

Main Results:

• Simulations demonstrated a resonance frequency tuning of 0.008 Hz/mV in the sub-1 Hz region.
• The force-balanced method effectively nulled mass displacement.
• Displacement was successfully obtained from the feedback force-generating voltage.

Conclusions:

• The proposed MEMS resonator with its multi-step electrical tuning and force-balanced method offers a viable solution for sub-1 Hz seismometers.
• This approach enables precise control over resonance frequency and improves device robustness.
• The findings pave the way for more sensitive and reliable seismic monitoring.