An out-of-plane electromagnetic induction based resonant MEMS magnetometer

Abstract

Abstract In this paper, an electromagnetic induction based resonant MEMS magnetometer used for out-of-plane magnetic field sensing is demonstrated. The main structure (named as 4S beam) includes four intercoupling equivalent oscillation elements composed of two S-shape folded beams and a long beam. The couple points between two adjacent oscillation elements are supported by beams whose end connects to the fixed anchors. When the 4S beam is electrostatically excited into the contractive-extensional (CE) mode, the closed area of induction coil patterned on the 4S beam changes with time and an induced electromotive force under amplitude modulation (AM) is generated across the output port according to the electromagnetic induction principle. The device is fabricated in batch by standard MEMS anodic bonding process. The whole interface circuit including the closed-loop self-oscillation and signal detection is established. The device operating in ambient pressure shows the overall magnetic field sensitivity of 1.306 mV/μT with 112 dB gain and can resolve minimum 2.57 μT magnetic field determined by the input noise density of 13.38 nV√Hz. In addition, the magnetometer registers extremely low power consumption of about 2.5μW, excellent linearity with the nonlinear error of 0.08%, and good temperature stability with TCS ≤ 506 ppm/℃. The above merits make this magnetometer very suitable for automotive industry, navigation systems and non-destructive testing.