Three-Axis Micofluxgate With a Fluxguide

A CMOS-compatible three-axis fluxgate chip was implemented and characterized in this paper. The thin-film fluxgate core was fabricated onto a silicon chip with integrated planar excitation and sensing coils. A nickel-zinc ferrite fluxguide was aligned and attached to the center of the chip to enable the out-of-plane sensitivity to the external field. The feature size of the microfluxgate chip with a fluxguide is 4.1 mm, and the minimum noise level is 5-7 nT/√Hz at 1 Hz for the in-plane sensing axis. When the sensor is operated in the second-harmonic mode, the optimal excitation frequency is around 50 kHz. The performance of the vector magnetometer for geomagnetic measurement is demonstrated by rotating the device in the earth's field and recording the azimuth response. The results showed that the proposed designs are valuable for simplifying the construction of miniature three-axis fluxgate, which is promising for applications in orientation determination and position detection, e.g., electronic compass and motion tracking.