Minimizing the effect of 1/f noise with a MEMS flux concentrator

To address the need for reducing the effect of 1/f noise on magnetic sensor performance we have invented a novel device, the MEMS flux concentrator, that shifts the operating frequency of magnetic sensors to higher frequencies. This is done by modulating the magnetic field before it reaches the sensor. The modulation is accomplished by putting the flux concentrators often used with magnetic sensors on MEMS structures. Flux concentrators enhance the magnetic field. In our present device, the magnetic sensor, a GMR sensor, is placed between flux concentrators that have been deposited on MEMS flaps. Depending on the design, the motion of the MEMS flaps modulates the field by a factor of 3 at frequencies from 8 to 15 kHz. Thus, the device shifts the operating frequency above the frequency region where 1/f noise dominates. This should increase the sensitivity of many magnetic sensors by two to three orders of magnitude. A perhaps equally important benefit is that because it is a modulation technique, it eliminates the problem of dealing with the large DC bias of most magnetoresistive sensors.