Magnetic Flux Vertical Motion Modulation for 1/${f}$ Noise Suppression in Magnetoresistance Field Sensors Using MEMS Device

Abstract

1/ $f$ noise is one of the main noise sources of magnetoresistance (MR) field sensors, which can cause intrinsic detection limit at low frequency. To suppress this noise, a novel magnetic flux vertical motion modulation (MFVMM) design using micro-electromechanical system flux concentrator (FC) and actuator is proposed in this paper, which can mitigate the 1/ $f$ noise by shifting the measurement frequency to kilohertz range. The proposed MFVMM has high efficiency and simple structure. The magnetic FC and the modulation film of MFVMM were analyzed with a numerical simulation. The simulation results show that the modulation efficiency of MFVMM exceeds 21%. A preliminary prototype sensor based on the multilayered giant MR AA002 and MFVMM was fabricated, and its modulation efficiency achieves 18.8% at a frequency of 7.01 kHz, which exceeds the efficiency of most existing sensors with the other modulation schemes. In addition, the magnetostatic detection ability is improved to 0.44 nT/ $\surd $ Hz.