Filter Bank Audio Distortion Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for testing audio equipment, such as analog to digital converters and amplifiers, fail to accurately measure time-varying harmonic and intermodulation distortion, particularly in non-mechanical systems, as they rely on static bias points and single frequency tones, which do not account for dynamic biasing and phase modulation effects.
Innovation Solution
The use of filter banks and multiple frequency signals to measure dynamic harmonic and intermodulation distortion, with a stairstep signal and arbitrary low frequency signals, allowing for the measurement of phase and frequency modulation effects by coupling these signals to phase detectors or frequency modulation detectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional single frequency tone tests are used, then measurement simplicity is maintained, but measurement precision of time-varying distortion is insufficient
Solution Approach 1:
The patent divides the frequency spectrum into multiple discrete frequency components using filter banks. Each filter in the bank isolates specific frequency ranges, allowing independent measurement of distortion at different frequencies. This segmentation enables comprehensive detection of time-varying distortion characteristics that single-frequency tests miss, while maintaining manageable system complexity through modular filter design.
Solution Approach 2:
The patent employs dynamic biasing signals that vary over time to modulate the operating point of the device under test. This dynamic approach allows the measurement system to capture time-varying distortion characteristics including modulation effects and transient behaviors. The system transitions from static single-point measurements to continuous dynamic characterization across multiple operating conditions.
2Adaptability or versatility
If static bias point measurements are used, then measurement simplicity is maintained, but adaptability to dynamic operating conditions is insufficient
Solution Approach 1:
The measurement system incorporates dynamic biasing signals that continuously vary the operating point of the device under test. This allows the system to adapt to and measure distortion characteristics across different operating conditions including modulation effects, transient responses, and time-varying behaviors. The dynamic approach captures real-world operating scenarios that static measurements cannot reveal.
Solution Approach 2:
The patent uses periodic modulation signals to dynamically vary the bias point of the device under test. These periodic variations enable the measurement of distortion at multiple operating points within a systematic framework. The periodic action allows comprehensive characterization of time-varying distortion while maintaining measurement coherence through regular signal patterns.
3Measurement precision
If conventional distortion measurements are used, then basic evaluation capability is maintained, but detection of phase modulation effects is insufficient
Solution Approach 1:
The patent introduces phase detectors and frequency modulation detectors as intermediary devices between the device under test and the measurement system. These detectors specifically extract phase and frequency modulation components from the output signal. The intermediary detectors convert subtle phase variations into measurable voltage or frequency signals, enabling precise detection of modulation effects that would otherwise be indistinguishable from ordinary distortion.
Solution Approach 2:
The measurement system segments the output signal into distinct frequency components using filter banks, then applies specific detection methods to each component. This segmentation allows targeted detection of phase modulation at different frequency ranges. By separating the signal spectrum and applying specialized detection to each band, the system achieves comprehensive phase modulation measurement without being overwhelmed by the complexity of analyzing the entire spectrum simultaneously.
Data Source
AI summary
A testing method or apparatus utilizes filter banks to measure time varying or dynamic harmonic distortion or intermodulation distortion. With a stairstep signal and filter banks, Nth order harmonic and or intermodulation distortion is measured via the filter banks at different offsets provided by an arbitrary low frequency signal. An amplifier with crossover distortion will show increased harmonic and or intermodulation distortion near the zero crossing while providing less distortion in other portions of the transfer curve of the amplifier.