Integrated micro search coil magnetometer

The μSCM integrates a search coil, calibrating coil, and INA on a single semiconductor die, optimizing planar spiral inductors to achieve high sensitivity and low noise, addressing the need for compact, energy-efficient low-frequency magnetic field measurements.

WO2026056785A1 Publication Date: 2026-03-19THE HONG KONG UNIV OF SCI & TECH
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Patent Information

Application Number
PCT/CN2025/119563
Authority / Receiving Office
WO · WO
Patent Type
Applications
Current Assignee / Owner
Priority Date
2024-09-10
Filing Date
2025-09-08
Publication Date
2026-03-19

AI Technical Summary

Technical Problem

Existing magnetometers are bulky and not compatible with CMOS technology, limiting their application in miniaturized devices, and there is a need for a compact, energy-efficient, and highly sensitive magnetometer for low-frequency magnetic field measurements.

Method used

A micro search coil magnetometer (μSCM) is developed with a search coil, calibrating coil, and instrumentation amplifier (INA) integrated on a single semiconductor die, utilizing planar spiral inductors and a nested-chopped current-feedback INA to mitigate flicker noise, enabling low-frequency magnetic field measurements.

Benefits of technology

The μSCM achieves high sensitivity with a noise equivalent magnetic field (NEMI) in the nT/√Hz range, providing a compact, energy-efficient solution for low-frequency magnetic field measurements, surpassing the performance of commercially available Hall effect sensors.

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Abstract

A fully integrated micro search coil magnetometer (μSCM) with a low-noise instrumentation amplifier is provided for low-frequency magnetic field measurements in the range of 1Hz to 1kHz. A micro search coil formed by stacking planar spiral inductors and serially connecting them with an in-phase configuration is used for magnetic field measurements. The critical line width and inner diameter of a planar spiral inductor are theoretically calculated and experimentally verified, enabling the development of a unique CMOS layout. This layout incorporates the calculated critical inner diameter, significantly optimizing the area utilization on the CMOS die. Additionally, the CMOS die includes a polysilicon-layer inductor for on-chip calibration, a Hall effect sensor for DC magnetic field measurement, and a temperature sensor for enhanced functionality. The μSCM delivers a compact, energy-efficient, and highly sensitive solution for low-frequency magnetic field measurements, surpassing the performance of most commercially available Hall effect sensors.
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