Initial studies on microelectromechanical system flux concentrators

To take advantage of the potential offered by the recent increase in the magnetoresistance of magnetic tunnel junctions, it is necessary to address the problem of 1∕f noise. ARL has been working on a device, the microelectromechanical system (MEMS) flux concentrator, that mitigates this problem by modulating the sensed magnetic field so that the sensor operates at a higher frequency region where the 1∕f noise is smaller. Initial results of testing the device are reported. Though the final step in the fabrication of the device appears to have adversely affected the MEMS motion, two important results were obtained. They are (1) applying the large amplitude voltage at kilohertz frequencies necessary to drive the MEMS structure does not increase the background noise and (2) even though the width of the drive voltage is several hertz, one can demodulate the signal using a lock-in amplifier in order to extract 1Hz modulation signals. This last result shows that the sensor can be used to detect slow moving or va...