Multi-Axis Magnetic Sensor Using Permanent Magnet Biasing
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Solution Overview
Problem
Existing magnetic field sensors face challenges in achieving three-axis sensing capability while minimizing power consumption and avoiding perming effects, which can lead to unstable device characteristics and noise, especially in applications requiring low cost and miniaturization.
Innovation Solution
A magnetic field sensor design incorporating strategically patterned permanent magnet layers to generate unique external bias fields for magnetoresistive sense elements, allowing for ultra-low power, multiple axis sensing without flux concentrators and inter-axis coupling, enabling efficient sensing of magnetic fields along X, Y, and Z axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional magnetic field sensor designs are used to achieve three-axis sensing capability, then sensing capability is improved, but power consumption increases and perming effects occur leading to unstable device characteristics
Solution Approach 1:
The sensor is divided into three independent sensing axes (X, Y, Z), each with its own magnetoresistive sense element and permanent magnet biasing structure. This segmentation allows each axis to operate independently with optimized power consumption, while collectively providing complete three-axis sensing capability.
Solution Approach 2:
Permanent magnet layers are pre-patterned during fabrication to generate the required bias fields for each sensing axis before the sensor operates. This preliminary action eliminates the need for continuous power consumption to maintain bias fields, as the permanent magnets provide stable biasing without external power.
2Measurement precision
If traditional magnetic field sensor designs are used to achieve three-axis sensing capability, then sensing capability is improved, but device stability deteriorates due to perming effects and noise
Solution Approach 1:
The patent extracts and eliminates the flux concentrators from the sensor design, using only magnetoresistive sense elements and permanent magnet biasing. This removal of flux concentrators eliminates the source of perming effects and associated noise, thereby improving device stability and reliability while maintaining three-axis sensing capability.
Solution Approach 2:
Each sensing axis employs locally optimized permanent magnet biasing structures with specific magnetization directions and patterns tailored to that axis. This local quality approach ensures optimal performance for each axis while avoiding the perming effects that arise from uniform or improper biasing configurations.
3Measurement precision
If complex sensor designs with flux concentrators are used, then three-axis sensing capability is achieved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the biasing function directly into the permanent magnet layers that are already part of the magnetoresistive sense element structure. By combining the biasing magnets with the sense elements and eliminating separate flux concentrator components, the design simplifies the manufacturing process while maintaining three-axis sensing capability.
Solution Approach 2:
The permanent magnet layers serve multiple functions: they provide bias fields for the magnetoresistive sense elements, define the sensing axes, and eliminate the need for separate flux concentrator components. This multi-functionality reduces the number of fabrication steps and components, thereby reducing manufacturing complexity.
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 achieves reliable, sensitive, and cost-effective three-axis magnetic field sensing with reduced power consumption and minimal perming effects, enhancing the sensitivity and reliability of the sensor while maintaining low manufacturing complexity.
Implementation Method 1
the permanent magnet layer magnetically biases the indeterminate magnetization state in an in-plane orientation to produce a first sense magnetization of the first sense layer and a second sense magnetization of the second sense layer
Implementation Method 2
A first magnetoresistive sense element is formed in the first leg, the first magnetoresistive sense element including a first pinned layer and a first sense layer
Data Source
AI summary
A magnetic field sensor for sensing an external magnetic field along a sensing direction comprises a sensor bridge. The sensor bridge has a first sensor leg that includes a first magnetoresistive sense element and a second sensor leg that includes a second magnetoresistive sense element. The first and second sense elements have respective a first and second pinned layers having corresponding first and second reference magnetizations. The second reference magnetization is oriented in an opposing direction relative to the first reference magnetization. The first and second sense elements have respective first and second sense layers, each having an indeterminate magnetization state. A permanent magnet layer is proximate the magnetoresistive sense elements. In the absence of an external magnetic field, the permanent magnet layer magnetically biases the indeterminate magnetization state of each sense layer in an in-plane orientation to produce a sense magnetization of the first and second sense layers.