A Xylophone Bar Magnetometer for micro/pico satellites

The Belgian Institute of Space Aeronomy (BIRA-IASB), "Centre Spatial
de Liège" (CSL), "Laboratoire de Techniques Aéronautiques et Spatiales"
(LTAS) of University of Liège, and the Microwave Laboratory of University
of Louvain-La-Neuve (UCL) are collaborating in order to develop a miniature
version of a xylophone bar magnetometer (XBM) using Microelectromechanical
Systems (MEMS) technology. The device is based on a classical resonating
xylophone bar. A sinusoidal current is supplied to the bar oscillating
at the fundamental transverse resonant mode of the bar. When an external
magnetic field is present, the resulting Lorentz force causes the bar to vibrate
at its fundamental frequency with an amplitude directly proportional to the
vertical component of the ambient magnetic field. In this paper we illustrate
the working principles of the XBM and the challenges to reach the required
sensitivity in space applications (measuring magnetic fields with an accuracy
of approximately of 0.1 nT). The optimal dimensions of the MEMS XBM are
discussed as well as the constraints on the current flowing through the bar.
Analytical calculations as well as simulations with finite element methods
have been used. Prototypes have been built in the Microwave Laboratory
using Silicon on Insulator (SOI) and bulk micromachining processes. Several
methods to accurately measure the displacement of the bar are proposed.