Resolution limit of anisotropic magnetoresistance(AMR) based vector magnetometer

Abstract

An AMR based vector magnetometer was developed for the Separated Payload program to explore the field-aligned currents in Earth polar region. It has the advantages of low volume and CubeSat platform compatible mass while still maintains adequate resolution. In order to determine the resolution limit of AMR based magnetometer, we measured the sensor’s intrinsic noise. This characteristic was in conflict with our prototype magnetoresistive magnetometer since phase sensitive detection(PSD) could only reject noise from interfacing circuit without affecting the signal to be measured. We believe that besides flipping the magnetization direction periodically, the set/reset technique also functions as a modulation to the magnetic field. The sensor operates at the modulation frequency and its noise level is much lower than that at low frequency. This technique is analyzed theoretically and a description from frequency perspective is given. By modulating the signal beyond corner frequency of the sensor and amplifier, both the sensor and interfacing circuit work in white noise region. Then we calculate the theoretical resolution limit of HMC1001 based magnetometer and the result shows that the noise floor is 24.9 pT/Hz0.5@1 Hz under 5 V bias with proper-matched amplifier.