Variable Load Circuit Reducing Magnetic Noise in Communication Devices
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Solution Overview
Problem
Extraneous magnetic fields produced by communication devices degrade the quality of audio signals transmitted to hearing aids, violating signal-to-noise ratio (SNR) regulations set by the FCC for hearing aid compatibility (HAC).
Innovation Solution
A communication device with a variable load circuit that selectively increases the root mean square (RMS) value of the time-varying current from its power source, reducing the ratio of peak to RMS current and thereby decreasing extraneous magnetic field strength, is implemented to improve the SNR of the magnetic field generated by the device's voice coil or telecoil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the communication device operates with standard current draw from the power source, then the device maintains normal operational energy levels, but extraneous magnetic fields are generated that degrade audio signal quality and violate HAC regulations
Solution Approach 1:
The patent applies dynamics by making the current draw variable rather than fixed. The power source is configured to provide time-varying current to the communication device, where the current magnitude is dynamically adjusted based on operational needs. This dynamic current management reduces extraneous magnetic field generation during periods when full power is not required, thereby improving audio signal quality without completely sacrificing operational energy levels.
Solution Approach 2:
The patent changes the parameter of current draw from a constant value to a variable value with different statistical characteristics. Specifically, it modifies the root mean square (RMS) value and peak-to-RMS ratio of the current. By adjusting these parameters, the extraneous magnetic field strength is reduced while maintaining adequate operational energy levels through proper current waveform management.
2Object-affected harmful factors
If the peak-to-RMS ratio of current from the power source is high, then the device operates with sufficient peak power, but extraneous magnetic field strength increases and degrades audio signal quality
Solution Approach 1:
The patent directly addresses this contradiction by changing the current waveform parameters. It reduces the peak-to-RMS ratio of the current drawn from the power source, which directly reduces extraneous magnetic field strength. The communication device is configured to operate with current waveforms that have optimized peak-to-RMS ratios, thereby reducing magnetic interference while maintaining sufficient average power levels for normal operation.
Solution Approach 2:
The patent employs periodic current delivery with specific waveform characteristics. By using time-varying current with controlled periodic patterns and optimized duty cycles, the system reduces peak current demands while maintaining adequate average power. This periodic action with optimized parameters reduces extraneous magnetic field generation while preserving necessary power availability.
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 ensures compliance with HAC requirements by reducing noise interference, enhancing the quality of audio signals received by hearing aids and maintaining the communication device's operational energy levels.
Implementation Method 1
A telecoil typically is implemented as an audio induction loop, such as a coil of wire, and may include a ferromagnetic core. The hearing aid telecoil is configured to detect a magnetic field containing audio signals generated by a loudspeaker voice coil or a telecoil of the communication device. More particularly, the hearing aid telecoil detects the energy of the magnetic field emanated by the communication device's loudspeaker voice coil or telecoil and transduces the energy to an electrical signal
Data Source
AI summary
Identifying an operation mode of a communication device in which the communication device is to comply with an interference requirement. In response to identifying the operation mode of the communication device in which the communication device is to comply with the interference requirement, reducing noise generated by the communication device by selectively increasing a root mean square (RMS) value of a time-varying current generated by a power source of the communication device.