Self-clocked dual-resonator micromachined Lorentz force magnetometer based on electromechanical sigma-delta modulation

This paper presents a new self-clocked dual-resonator Lorentz force magnetometer, based on dual quantization electromechanical sigma-delta modulation (EM-ΣΔM) closed-loop operation. The magnetometer comprises a matched pair of resonators on the same silicon die. The first resonator is operated in a self-sustaining oscillation to generate the Lorentz drive current and all internal circuit clocks based on a self-clocking scheme. The second resonator is operated in a high order EM-ΣΔM force feedback loop to measure magnetic field. The circuit system is implemented in hardware based on FPGA. The results demonstrate the proposed design significantly reduced the offset and drift compared to open loop operation. The proposed design achieved 7X improvement in bias instability (increasing the averaging time to reach the bias instability from 1s to 8s). The bandwidth is increased by a factor of 16, reaching ∼80Hz, independent of the mechanical bandwidth of 5Hz.