Crosstalk Mitigation via Band-Corrected Impedance
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Solution Overview
Problem
Crosstalk between audio channels is a significant issue in multichannel audio systems, particularly when audio transducers share a common ground return path, leading to unwanted signal interference and requiring effective mitigation techniques.
Innovation Solution
An audio driver circuit with a crosstalk compensation block that generates compensation signals based on predetermined impedance values and measured DC impedance values modified by a band correction factor, applied to each audio signal path to minimize crosstalk across the frequency band, using impedance and inductance measurements for accurate impedance estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If DC impedance value is used for crosstalk compensation, then the compensation function is simple, but the compensation accuracy is poor when DC impedance is not representative of mean impedance over frequency band
Solution Approach 1:
The patent transforms the single DC impedance parameter into multiple frequency-point impedance parameters (first, second, third impedance values at different frequencies). By measuring impedance at multiple frequency points and calculating their average, the system obtains a more accurate mean impedance value that better represents the actual impedance characteristics across the frequency band, thereby improving crosstalk compensation accuracy without excessive complexity increase
Solution Approach 2:
The patent replaces the simple DC resistance measurement approach with an AC impedance measurement system that operates at multiple frequency points. This substitution enables the system to capture the frequency-dependent characteristics of the audio load, providing a more accurate representation of the mean impedance that DC measurement alone cannot provide
2Measurement precision
If multiple impedance measurement points are used to estimate mean impedance, then the impedance estimation accuracy is improved, but the measurement complexity increases
Solution Approach 1:
The patent measures impedance at three specific frequency points (first, second, and third frequencies) and calculates the mean impedance as the average of these three values. This approach provides improved accuracy over single-point DC measurement while maintaining reasonable system complexity by using a fixed, small number of measurement points rather than continuous frequency sweeping
Solution Approach 2:
The patent performs preliminary impedance measurements at multiple frequency points before the actual audio playback. These pre-measured impedance values are stored and used to calculate the mean impedance, which then informs the crosstalk compensation function during audio operation. This preliminary action separates the measurement phase from the playback phase, simplifying the real-time processing requirements
Data Source
AI summary
This application describes methods and apparatus for mitigating the effects of crosstalk in multichannel audio. An audio driver circuit (200) for driving first and second audio loads (103) having a common return path (RC), has first and second signal paths (Left and Right). A crosstalk compensation block (205) is configured to add a first compensation signal to the first signal path and add a second compensation signal to the second signal path. The first compensation signal is generated based on the second audio signal and a first compensation function and the second compensation signal is generated based on the first audio signal and a second compensation function. Each of the first and second compensation functions is based on a predetermined impedance value for at least part of the common return path (RH1) and is also based on a determined DC impedance value (ZL, ZR) for one of the first and second audio loads which is modified by a band correction factor (γ). The band correction factor modifies the DC impedance value so it is a better estimate of impedance across the frequency band of interest.