TMR Vortex Sensor Layout for Misalignment-Robust Back Bias Sensing
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Solution Overview
Problem
Magnetic sensors face limitations such as excessive size, inadequate sensitivity and dynamic range, high cost, reliability issues, and sensitivity degradation due to positional misalignment of magnetic sensing elements.
Innovation Solution
The use of TMR vortices in a back bias sensor layout, where TMR vortices are arranged along a common line aligned with the horizontal symmetry axis of a back bias magnet, forming bridge circuits to enhance signal-to-noise ratio, reduce susceptibility to stray fields, and improve robustness to misplacement and tower asymmetry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional magnetic sensor layouts are used, then the sensor can detect magnetic fields, but the sensor footprint is excessive and sensitivity is inadequate
Solution Approach 1:
The sensor is divided into multiple TMR vortex elements arranged in a bridge configuration, where each element contributes to the overall sensing capability. This segmentation allows for improved sensitivity through differential measurement while maintaining a compact footprint by sharing the magnetic field sensing region among multiple elements.
Solution Approach 2:
The patent transitions from planar sensor layouts to a three-dimensional bridge configuration where TMR vortex elements are arranged in multiple dimensions. This spatial arrangement enables better magnetic field coverage and sensitivity enhancement without proportionally increasing the sensor footprint, as the elements leverage vertical and diagonal spacing.
2Measurement precision
If magnetic sensing elements are positioned to maximize sensitivity, then measurement precision improves, but positional misalignment degrades sensor performance
Solution Approach 1:
Each TMR vortex element in the bridge configuration has its magnetization orientation specifically oriented to be sensitive to the magnetic field component in the desired direction. The reference layers are magnetized perpendicular to the sensing direction, creating local magnetic structures that provide both high sensitivity and inherent alignment tolerance through the bridge differential measurement.
Solution Approach 2:
The bridge configuration provides inherent feedback through differential measurement, where the output is the difference between opposite sides of the bridge. This differential feedback mechanism automatically compensates for common-mode disturbances and misalignment effects, as symmetric misalignments produce equal and opposite errors that cancel in the differential output.
3Adaptability or versatility
If the sensor uses a back bias magnet arrangement, then the sensor can detect moving ferromagnetic objects, but the sensor is susceptible to stray fields and tower asymmetry
Solution Approach 1:
The patent introduces asymmetry in the bridge configuration by positioning TMR vortex elements at specific locations relative to the back bias magnet, with alternating magnetization orientations. This asymmetric arrangement creates a magnetic field distribution that enhances detection of moving ferromagnetic objects while the differential bridge measurement compensates for symmetric stray field disturbances.
Solution Approach 2:
The patent converts the potentially harmful effect of the back bias magnet's magnetic field into a beneficial sensing mechanism. By carefully designing the bridge configuration and magnetization orientations, the static magnetic field from the back bias magnet becomes the operating point for the TMR vortices, while the dynamic response to moving ferromagnetic objects is extracted through differential measurement, effectively turning the bias field into part of the sensing mechanism.
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 TMR vortex layout achieves a smaller footprint, higher signal-to-noise ratio, improved immunity to stray fields, and increased robustness to misalignment, enabling applications like cam sensing, crank sensing, and transmission speed sensing with enhanced performance.
Implementation Method 1
a plurality of sensing element groups disposed at different locations on a surface of the substrate and laid out along a common line aligned with the horizontal symmetry axis of the back bias magnet, each of the plurality of sensing element groups having one or more tunneling magnetoresistance (TMR) vortices
Implementation Method 2
a back bias magnet arranged to generate a bias field at least having components in a plane parallel to a surface of the substrate, the bias field having a horizontal symmetry axis within the plane
Data Source
AI summary
According to one aspect of the disclosure, a sensor includes a substrate; a back bias magnet arranged to generate a bias field at least having components in a plane parallel to a surface of the substrate, the bias field having a horizontal symmetry axis within the plane; and a plurality of sensing element groups disposed at different locations on a surface of the substrate and laid out along a common line aligned with the horizontal symmetry axis of the back bias magnet, each of the plurality of sensing element groups having one or more tunneling magnetoresistance (TMR) vortices having an axis of maximum sensitivity aligned with the common line.