Magnetic Flux Synchronous Motion Modulation for Improving the Low-Frequency Magnetic Field Detection Limit of Magnetoresistive Sensor Using MEMS Resonators

MEMS-based magnetoresistive (MR) sensors have attracted considerable attention for years due to their small weight, low power consumption, and high sensitivity, whereas the 1/ $f$ noise is larger in the low-frequency region and degrades the low-frequency magnetic field detection limit. To reduce the impact of 1/ $f$ noise, MEMS resonators are utilized to modulate the low-frequency field to a high-frequency region where the 1/ $f$ noise vanishes. This article proposes a novel modulation method called synchronous motion modulation (SMM) using a comb-driven resonator and a piezoelectric cantilever resonator; meanwhile, it analyzes the relationship of modulation efficiency of SMM, vertical motion modulation (VMM), and gap change modulation (GCM) theoretically and with finite element method (FEM) simulation. It is found that the theoretical analysis is coincident with numerical simulation, and the SMM is the optimal modulation method for improving the low-frequency magnetic field detection limit due to its modulation efficiency is the sum of that of VMM and GCM.