Magnetic Sensor Modulation for Low-Frequency Detection

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Solution Overview

Problem

Existing magnetic sensors face challenges in detecting low-frequency magnetic fields with high sensitivity due to significant 1/f noise, and they require large currents to saturate the magnetosensitive elements, leading to inefficiencies.

Innovation Solution

A magnetic sensor design that includes a sensor chip with magnetosensitive elements, a magnetic field collecting body, and an excitation coil, where a modulation circuit supplies a frequency-specific excitation current to periodically saturate the magnetosensitive elements without saturating the magnetic field collecting body, using a configuration that reduces 1/f noise and current consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a current line for saturating the magnetosensitive element is disposed near the magnetic sensor, then the magnetosensitive element can be saturated, but a large current is required which increases energy consumption

Engineering Contradiction:

Improvesaturation of magnetosensitive elementVSAvoidcurrent consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent introduces a magnetic field collecting body as an intermediary component between the excitation coil and the magnetosensitive element. This mediator concentrates and directs the magnetic field generated by the excitation coil, enabling effective saturation of the magnetosensitive element with reduced current. The magnetic field collecting body acts as a magnetic conduit that amplifies the magnetic field intensity at the target location without requiring proportionally higher current input.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the spatial distribution and intensity parameters of the magnetic field by introducing the magnetic field collecting body. This component alters the magnetic field geometry to concentrate flux lines at the magnetosensitive element, effectively changing the field distribution parameters to achieve saturation with lower current requirements.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If the frequency of the magnetic field to be measured becomes lower, then detection becomes more challenging, but 1/f noise becomes more conspicuous which reduces S/N ratio

Engineering Contradiction:

Improvedetection sensitivityVSAvoid1/f noise

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies periodic action by using an excitation coil to periodically saturate the magnetosensitive element at a specific frequency. This periodic saturation creates a modulation effect that shifts the detection frequency away from the problematic low-frequency region where 1/f noise dominates. By operating in a higher frequency regime through periodic excitation, the system achieves better S/N ratio while still detecting low-frequency magnetic fields through the modulated response.

Inventive Principle:

Principle #19Periodic action

3Reliability

If large current is used to saturate the magnetosensitive element, then saturation is achieved, but current consumption increases which reduces efficiency

Engineering Contradiction:

Improvesaturation levelVSAvoidenergy consumption

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The magnetic field collecting body serves as an intermediary that efficiently transfers magnetic field energy from the excitation coil to the magnetosensitive element. This mediator reduces energy losses in the magnetic path and ensures that magnetic field intensity is concentrated precisely where needed, achieving saturation with minimal energy input and reducing overall energy consumption.

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The design effectively reduces 1/f noise and current consumption while maintaining high sensitivity for low-frequency magnetic field detection, allowing efficient and accurate magnetic field collection.

Implementation Method 1

an excitation coil wound around the magnetic field collecting body; and a modulation circuit that supplies an excitation current having a predetermined frequency to the excitation coil

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

a magnetic field collecting body for collecting a magnetic field to the magnetosensitive element

Methodology Applied

Scientific EffectMagnetic flux concentration: Magnetic Field

Implementation Method 3

periodically magnetically saturate the magnetosensitive element

Methodology Applied

Scientific EffectMagnetic saturation: Magnetic Saturation

Data Source

PatentUS20250264552A1Magnetic sensor

Publication Date: 2025.08.21 TDK CORP

AI summary

Disclosed herein is a magnetic sensor that includes a sensor chip having a magnetosensitive element, a magnetic field collecting body for collecting a magnetic field to the magnetosensitive element, an excitation coil wound around the magnetic field collecting body, and a modulation circuit that supplies an excitation current having a predetermined frequency to the excitation coil so as to periodically magnetically saturate the magnetosensitive element without magnetically saturating the magnetic field collecting body.