A Lorentz Force Magnetometer based on a TPoS Resonator Operating in Close-loop Configuration

Lorentz force magnetometer (LFM) holds promise for monolithic integration with micro-accelerometer and micro-gyroscope. However, piezoelectric LFMs reported so far can only operate in open-loop configuration, which adds to the complexity and power consumption of interface circuits. This work reports the first piezoelectric LFM operating in close-loop configuration, which is realized by using a thin-film piezoelectric on silicon (TPoS) resonator as the core in an oscillator. The output frequency of the oscillator tracks the natural frequency of the resonator, which is frequency-modulated by the external magnetic field to be measured. The proposed LFM exhibits high relative magnetic sensitivity of 82.9 ppm/mT and is able to detect x- or y-axis magnetic fields by reconfiguring the bias current paths. Due to the high magnetic sensitivity and easy interface circuit, the proposed piezoelectric LFM is promising for realizing TPoS-based monolithic integration of accelerometer, gyroscope and magnetometer.