Magnetic Sensor Annular Structures Modulate Low Frequency Detection
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Solution Overview
Problem
Magnetic sensors face challenges in detecting weak magnetic fields in low frequency regions due to high 1/f noise, which existing technologies have not adequately addressed, especially when noise from the magnetosensitive element is modulated.
Innovation Solution
A magnetic sensor design featuring first and second magnetic structures with annular shapes and excitation coils, where the current flowing in these coils modulates the detection signal, reducing 1/f noise and allowing for high sensitivity in low frequency magnetic field detection, with symmetric arrangement and a magnetoresistance effect element to enhance sensitivity and reduce noise application to the magnetosensitive element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetosensitive element is used to detect weak magnetic fields, then detection capability is improved, but 1/f noise increases and reduces S/N ratio in low frequency regions
Solution Approach 1:
The patent applies periodic action by using AC excitation currents with predetermined frequencies to drive the magnetic structures, which modulates the detection signal at a frequency higher than the low frequency region being measured. This periodic excitation shifts the detection signal away from the noisy low frequency region where 1/f noise dominates, enabling high sensitivity detection of weak magnetic fields in low frequency regions despite the presence of 1/f noise in the magnetosensitive element.
2Measurement precision
If current is used to modulate the detection signal for reducing 1/f noise, then low frequency detection sensitivity is improved, but noise from the magnetosensitive element is also modulated
Solution Approach 1:
The patent introduces magnetic structures with high magnetic permeability as intermediaries between the external magnetic field and the magnetosensitive element. These magnetic structures concentrate and guide magnetic flux, enhancing the magnetic field applied to the magnetosensitive element while the AC excitation currents modulate this enhanced field. The intermediary magnetic structures thus enable effective signal modulation while managing the noise characteristics of the magnetosensitive element.
3Measurement precision
If magnetic structures are arranged symmetrically with respect to the magnetosensitive element, then magnetic field application to the element is reduced, but detection of weak magnetic fields is improved
Solution Approach 1:
The patent employs asymmetric arrangement of magnetic structures relative to the magnetosensitive element. The magnetic structures are positioned at different locations and orientations to create an asymmetric magnetic flux distribution that concentrates magnetic flux onto the magnetosensitive element. This asymmetric configuration optimizes the magnetic field application to enhance detection sensitivity for weak magnetic fields while managing the overall magnetic field environment.
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 enables high sensitivity detection of low frequency magnetic fields by modulating the detection signal with a predetermined frequency current, reducing 1/f noise and minimizing noise application to the magnetosensitive element, thereby improving detection accuracy and efficiency.
Implementation Method 1
a first excitation coil wound around the first magnetic structure; and a second excitation coil wound around the second magnetic structure
Implementation Method 2
a magnetosensitive element disposed on a magnetic path formed by the magnetic gap and has a sensitivity axis in the first direction
Data Source
AI summary
Disclosed herein is a magnetic sensor that includes first and second magnetic structures each having an annular structure and arranged in a first direction with a magnetic gap interposed therebetween, a magnetosensitive element disposed on a magnetic path formed by the magnetic gap and has a sensitivity axis in the first direction, a first excitation coil wound around the first magnetic structure, and a second excitation coil wound around the second magnetic structure.