Magnetoimpedance Sensor Knee-Biasing for Low-Noise Field Detection
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Solution Overview
Problem
Existing magnetoimpedance sensors face challenges in achieving high sensitivity and low noise while maintaining a compact size, particularly in detecting RF magnetic fields, due to magnetic hysteresis and linear regions of the B-H curve.
Innovation Solution
The solution involves using paired magnetoimpedance sensors biased into opposite knee regions of the B-H curve, with a radio frequency choke to limit outputs to non-linear regions, and a synchronous detector to convert asymmetrical signals into a DC voltage indicative of the applied magnetic field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetoimpedance sensors use ferromagnetic materials to detect magnetic fields, then sensitivity to magnetic field changes is improved, but magnetic hysteresis causes noise and reduces measurement precision
Solution Approach 1:
The patent applies asymmetry by biasing the magnetoimpedance sensors into opposite knee regions of the B-H curve. This asymmetric positioning exploits the non-linear regions where the slope is steepest, creating differential signals that cancel out common-mode hysteresis effects while preserving sensitivity to external magnetic field changes.
Solution Approach 2:
The patent changes the operating parameters by applying a DC bias current to position the sensors at specific points (knee regions) on the B-H curve. This parameter adjustment transforms the sensors from operating in linear regions to operating in non-linear regions with maximum slope, thereby optimizing sensitivity while managing hysteresis through differential measurement.
2Volume of moving object
If magnetoimpedance sensors are made physically compact for environmental robustness, then device size is reduced, but sensitivity and signal strength deteriorate
Solution Approach 1:
The patent merges two compact magnetoimpedance sensors into a differential configuration, connecting them in series with opposite polarities. This combination allows each sensor to remain physically small while the paired arrangement amplifies the differential signal response to external magnetic fields, maintaining sensitivity despite reduced individual sensor size.
Solution Approach 2:
The patent employs composite material structures by combining ferromagnetic core materials with non-magnetic winding materials in a structured configuration. This composite approach enables compact sensor design while maintaining the magnetic properties necessary for high sensitivity detection through the magnetoimpedance effect.
3Measurement precision
If magnetoimpedance sensors operate in linear regions of the B-H curve, then output stability is improved, but sensitivity to magnetic field changes is reduced
Solution Approach 1:
The patent inverts the conventional approach by deliberately operating in the non-linear knee regions of the B-H curve rather than in the linear regions. This inversion exploits the steepest slope portions of the curve where sensitivity is maximized, and uses differential pairing to manage the stability concerns through common-mode rejection of hysteresis effects.
Solution Approach 2:
The patent applies periodic AC excitation signals to the magnetoimpedance sensors, causing the magnetic flux to oscillate through the knee regions of the B-H curve. This periodic action through the non-linear regions maximizes the differential signal response to external magnetic fields while the synchronous detection process extracts the relevant information with high precision.
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
This approach enhances sensitivity and reduces noise by focusing on the non-linear knee regions of the B-H curve, providing accurate and precise magnetic field detection.
Implementation Method 1
Magnetoimpedance generally addresses changes of impedance of a material when an external magnetic field is applied to the material. Impedance changes may be observed to determine values of the fluctuations in an applied magnetic field.
Implementation Method 2
Ferromagnetic materials can exhibit magnetic hysteresis, which is often considered to be the lag a magnetic material demonstrates when becoming magnetized and demagnetized upon being exposed to an applied changing external magnetic field.
Data Source
AI summary
Applied magnetic fields are evaluated using portions of the B-H curve of a material exposed to the applied magnetic field. The portions of the B-H curve being evaluated may reside near the top and bottom of the curve where non-linear results in the curve occur. Selective sampling of nonlinear regions of the B-H curve are performed to determine the direction and strength of the applied magnetic field.