XMR Sensor Jitter Reduction via Segmented Stack Design
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Solution Overview
Problem
XMR sensors are sensitive to magnetic fields orthogonal to their sensing direction, leading to increased jitter due to imprecise positioning, which is a challenge in applications like automotive speed detection and tire pressure monitoring.
Innovation Solution
A device comprising two independent XMR sensor stacks, each with a free layer and a reference layer, electrically coupled to operate as a single element, with a distance of 15 nm or more between their free layers, sharing one or more layers such as an antiferromagnetic layer, to reduce jitter by canceling out orthogonal magnetic field influences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If XMR sensors are used for magnetic field detection, then measurement precision is improved compared to Hall sensors, but sensitivity to orthogonal magnetic fields causes jitter to increase
Solution Approach 1:
The sensor is divided into multiple independent XMR sensor stacks (at least two) that are electrically coupled to operate together. Each stack independently detects magnetic fields, and their combined output statistically cancels orthogonal field influences, reducing jitter by a factor of 1/√n where n is the number of stacks.
Solution Approach 2:
Multiple independent XMR sensor stacks are electrically coupled and merged into a single operational element. The stacks share common layers (such as antiferromagnetic layers) while maintaining independent sensing capabilities, combining their outputs to achieve jitter reduction while maintaining the benefits of XMR technology.
2Ease of operation
If imprecise positioning of XMR sensors occurs, then ease of installation is improved, but measurement precision deteriorates due to increased jitter
Solution Approach 1:
The sensor comprises multiple independent stacks that can be positioned with standard tolerances. The segmentation allows each stack to independently handle positioning variations, and their combined statistical processing compensates for imprecise positioning, maintaining measurement precision despite relaxed positioning requirements.
Solution Approach 2:
The patent converts the harmful effect of orthogonal magnetic field sensitivity into a benefit by using statistical cancellation. The same sensitivity that causes jitter in single sensors becomes useful when multiple sensors are combined, as the random variations cancel out, turning positioning imprecision and orthogonal sensitivity into opportunities for statistical error reduction.
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 solution effectively reduces jitter by a factor of 1/√n, where n is the number of stacks, improving the accuracy of magnetic field measurements by statistically canceling out orthogonal magnetic field effects.
Implementation Method 1
XMR sensors are based on one or more magnetoresistive (MR) effects
Implementation Method 2
sharing one or more layers, such as an antiferromagnetic layer
Data Source
AI summary
Sensor devices and methods are provided where a second magnetoresistive sensor stack is provided on top of a first magnetoresistive sensor stack.