Magnetic Sensor Angle and Field Strength Detection

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Solution Overview

Problem

Conventional magnetic sensors using magnetic tunnel junction elements face challenges in accurately determining the angle and magnitude of an external magnetic field due to issues with magnetic anisotropy and sensitivity, which limits their ability to detect both the angle and strength of the magnetic field simultaneously.

Innovation Solution

A magnetic sensor system comprising a combination of angle sensors and magnetic field strength sensors, where the angle sensors utilize a plurality of first magnetoresistive elements with fixed reference layers and free layers that change magnetization direction with the external field, and the field strength sensors use second magnetoresistive elements with vortically magnetized free layers, allowing for the detection of both the angle and strength of the magnetic field based on unique output characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single magnetic tunnel junction element is used for angle detection, then the device complexity is reduced, but the measurement precision of magnetic field angle and magnitude is insufficient

Engineering Contradiction:

Improvesensor structureVSAvoidmagnetic field detection accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The sensor is divided into two functional segments: an angle sensor portion with magnetoresistive elements having in-plane magnetization for detecting field angle, and a magnitude sensor portion with magnetoresistive elements having perpendicular magnetization for detecting field magnitude. This segmentation allows each portion to be optimized for its specific function, resolving the contradiction between simple structure and high measurement precision.

Inventive Principle:

Principle #1Segmentation

2Measurement precision

If magnetic tunnel junction elements with fixed reference layers are used, then the angle detection capability is improved, but the ability to detect magnetic field strength is deteriorated

Engineering Contradiction:

Improveangle detection accuracyVSAvoidmagnetic field detection capability

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The sensor system achieves multi-functionality by combining two types of magnetoresistive elements with different magnetization orientations. The angle sensor portion with in-plane magnetization elements detects field angle, while the magnitude sensor portion with perpendicular magnetization elements detects field magnitude. This universal design allows a single integrated sensor to perform both angle and magnitude detection, resolving the contradiction between specialized angle detection capability and overall detection versatility.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Device complexity

If conventional angle sensor structures are used, then the device simplicity is maintained, but the nonlinearity in output characteristics increases

Engineering Contradiction:

Improvesensor configurationVSAvoidoutput characteristic linearity

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

Different regions of the sensor have different magnetic anisotropy properties tailored to their specific functions. The angle sensor portion uses elements with in-plane magnetization that provide linear cosine output characteristics for angle detection, while the magnitude sensor portion uses elements with perpendicular magnetization that provide linear output characteristics for magnitude detection. This local optimization of magnetic properties resolves the contradiction between device simplicity and output linearity.

Inventive Principle:

Principle #3Local quality

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 system enables precise detection of the angle and strength of the external magnetic field by utilizing distinct output characteristics from the angle and field strength sensors, providing improved accuracy and reducing nonlinearity, thus overcoming the limitations of conventional sensors.

Implementation Method 1

a first sensor and a second sensor each including a plurality of first magnetoresistive elements 111 to 116, 211 to 216

Methodology Applied

Scientific EffectMagnetoresistance effect: Magnetoresistance

Implementation Method 2

the magnetic field strength sensor has different output characteristics in accordance with the angle between the direction of the external magnetic field and the reference direction

Methodology Applied

Scientific EffectMagnetic vortex:

Data Source

PatentUS11774524B2Magnetic sensor, magnetic sensor array, magnetic field distribution measurement device, and position identification device

Publication Date: 2023.10.03 MURATA MFG CO LTD

AI summary

A magnetic sensor includes an angle sensor including first magnetoresistive elements and producing an output based on an angle between a direction of an external magnetic field and a reference direction, and a magnetic field strength sensor including second magnetoresistive elements and producing an output based on a strength of the external magnetic field. The angle sensor and the magnetic field strength sensor have a same or substantially a same direction of normal to a reference surface for sensor formation. The magnetic field strength sensor has different output characteristics in accordance with the angle between the direction of the external magnetic field and the reference direction. Based on the angle between the direction of the external magnetic field and the reference direction detected by the angle sensor and the output from the magnetic field strength sensor, the strength of the external magnetic field is determined.