EXPLOITATION OF NONLINEAR EFFECTS FOR ENHANCEMENT OF THE SENSING PERFORMANCE OF RESONANT SENSORS
Seungkeun Choi, Seong-Hyok Kim, Yong-Kyu Yoon and Mark Allen
Nonlinear effects in resonating structures have been exploited to achieve high sensing performance. The nominal platform consists of a disc type resonant magnetic sensor, comprising a permanent magnet supported by multiple micromachined silicon beams. Nonlinearity effects on sensitivity have been characterized as a function of beam width and the number of beams using analytical models as well as numerical analysis. By increasing the number of beams while reducing beam width (and thereby maintaining constant nominal linear resonant frequency), large nonlinearity has been obtained, resulting in increased change in operating resonant frequency per unit applied magnetic field. To verify the result experimentally, magnetic sensors with differing beam dimensions are microfabricated and tested. As expected, a structure with 6 beams and a beam width of 13.1 mum shows a higher normalized sensitivity of 0.196 [mHz/Hz-degree] than one with 4 beams and a beam width of 14.6 mum of 0.086 [mHz/Hz-degree] in detection of the direction of the magnetic field of the earth.
Keywords: FEM simulation, MEMS, magnetic sensor, nonlinear effects and resonant sensors