Low-frequency noise characterization of a magnetic field monitoring system using an anisotropic magnetoresistance

TL;DR

This paper evaluates anisotropic magnetoresistive sensors for low-frequency magnetic field monitoring in space, analyzing noise reduction techniques and comparing their performance to fluxgate magnetometers used in space missions.

Contribution

It demonstrates the suitability of AMR sensors for space applications and explores effective noise reduction methods for low-frequency magnetic measurements.

Findings

AMR sensors exhibit comparable noise levels to fluxgate magnetometers in the 0.1 mHz to 1 Hz range.

Conventional modulation techniques do not reduce 1/f noise, necessitating alternative methods.

Signal conditioning noise contributions can be minimized through analysis and design improvements.

Abstract

A detailed study about magnetic sensing techniques based on anisotropic magnetoresistive sensors shows that the technology is suitable for low-frequency space applications like the eLISA mission. Low noise magnetic measurements at the sub-millihertz frequencies were taken by using different electronic noise reduction techniques in the signal conditioning circuit. We found that conventional modulation techniques reversing the sensor bridge excitation do not reduce the potential $1/f$ noise of the magnetoresistors, so alternative methods such as flipping and electro-magnetic feedback are necessary. In addition, a low-frequency noise analysis of the signal conditioning circuits has been performed in order to identify and minimize the different main contributions from the overall noise. The results for chip-scale magnetoresistances exhibit similar noise along the eLISA bandwidth ($0.1\,{\rm mHz}-1\,{\rm Hz}$) to the noise measured by means of the voluminous fluxgate magnetometers used in its precursor mission, known as LISA Pathfinder.