A micromachined magnetometer with frequency modulation at the output

Abstract

A novel design of a resonant magnetic field sensor and complete modeling of its behavior are presented along with a description of the experimental set up and results. The sensor output is a shift in frequency, which is robust against interference and easy to be read by digital systems. An analytic model is derived for the sensor behavior using novel and existing techniques. This model takes advantage of the ability of Dunkerley's method to model complex structures. Devices were fabricated in an SOI bulk micromachining process. Experimental results for the performance of the devices are in good agreement with modeling predictions. The minimum detected field is 80muT with simple electronics. However, the theoretical minimum detectable signal for different devices is on the order of 10's of nano-teslas at 1Torr measured with a noiseless spectrum analyzer with a 100Hz bandwidth. This level of sensitivity is a consequence of the frequency modulation of the output signal