Compensation Coil for Magnetic Interference Attenuation
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Solution Overview
Problem
Electronic systems, such as smartphones, face significant performance degradation due to electromagnetic interference (EMI) from components like voice coils, leading to large magnetic compass heading errors, which affect navigation and gaming applications.
Innovation Solution
A compensation coil is placed underneath the magnetic field sensor, driven by a reverse current generator coupled to the power supply of the EMI source, generating a counter magnetic field to attenuate EMI in the frequency band overlapping with the sensor's operating frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a voice coil is integrated within the same housing as a digital magnetic compass, then the electronic system achieves compact integration and functional versatility, but electromagnetic interference causes large magnetic compass heading errors and performance degradation
Solution Approach 1:
A compensation coil is introduced as an intermediary component between the voice coil (EMI source) and the magnetic compass sensor. This compensation coil generates a counter magnetic field that actively cancels the interfering magnetic field from the voice coil, thereby protecting the magnetic compass from heading errors while allowing both components to coexist in the same housing
Solution Approach 2:
The harmful electromagnetic interference from the voice coil is converted into a beneficial effect by using the same power supply to drive both the voice coil and compensation coil. The compensation coil utilizes the power supply signals to generate an opposing magnetic field that precisely counteracts the interference, transforming the EMI problem into a solution that enables compact integration
2Measurement precision
If EMI sources are deactivated to eliminate interference, then magnetic field measurement accuracy improves, but system functionality is reduced
Solution Approach 1:
Instead of deactivating EMI sources, the system applies preliminary anti-action by continuously generating a counter magnetic field from the compensation coil that preemptively cancels the interfering field before it affects the magnetic compass. This allows EMI sources to remain active while maintaining measurement accuracy
Solution Approach 2:
The system employs feedback by monitoring the power supply signals that drive the EMI sources and using these same signals to control the compensation coil. The compensation coil responds in real-time to the EMI source activity, dynamically adjusting the counter magnetic field to maintain measurement accuracy while EMI sources remain operational
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 solution effectively reduces EMI by up to 80% in the audio frequency band, allowing accurate magnetic field measurements and minimizing heading errors, thus enhancing the performance of navigation and gaming applications without deactivating EMI sources.
Implementation Method 1
A compensation coil is placed underneath the magnetic field sensor, driven by a reverse current generator coupled to the power supply of the EMI source, generating a counter magnetic field to attenuate EMI
Implementation Method 2
A compensation coil is placed underneath the magnetic field sensor, driven by a reverse current generator
Data Source
AI summary
A compensation coil placed at least partially underneath a magnetic field sensor package in an electronic system provides attenuation of electromagnetic interference (EMI). In an embodiment, the compensation coil attenuates EMI in a frequency band which overlaps with an operating frequency band of the magnetic field sensor. This allows the magnetic field sensor to make accurate magnetic field measurements in the presence of system level alternating current (AC) EMI. In an embodiment, a system comprises: a magnetic field sensor; a compensation coil placed at least partially underneath the magnetic field sensor; and a reverse current generator coupled to the compensation coil and to a power supply that is coupled to an electromagnetic interference (EMI) source, the reverse current generator operable to generate a reverse current in the compensation coil to generate a counter magnetic field for compensating the EMI.