Audio Distortion Testing for Dynamic Bias and Phase Modulation
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 fixed bias points and single-tone tests, which do not account for dynamic biasing and phase modulation effects.
Innovation Solution
The use of filter banks and arbitrary low-frequency signals with stairstep or multiple-step signals to measure Nth order harmonic and intermodulation distortion, allowing for dynamic distortion analysis by coupling multiple frequencies into the device under test and employing phase or frequency modulation detectors to assess induced phase and frequency modulation effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional harmonic and intermodulation distortion tests are used with zero offset signal, then basic distortion performance can be measured, but time-varying and dynamic distortion effects remain undetected
Solution Approach 1:
The patent applies dynamics by transitioning from static zero-offset testing to dynamic biasing where the test signal includes a time-varying offset component. This allows the measurement system to capture distortion characteristics that change with bias conditions, enabling detection of time-varying harmonic and intermodulation distortion that conventional static methods miss.
Solution Approach 2:
The invention changes the bias parameter from fixed zero-offset to dynamic time-varying offset. By modulating the bias condition during measurement, the system can observe how distortion products vary with bias level, providing insight into dynamic performance characteristics of audio equipment that static measurements cannot reveal.
2Ease of operation
If single-tone tests are used for simplicity, then basic performance can be assessed, but phase modulation effects and frequency variations remain undetected
Solution Approach 1:
The patent employs periodic action by using multiple tones with specific frequency relationships (e.g., closely spaced tones) that create periodic modulation patterns. This allows phase modulation effects and frequency variations to manifest as detectable periodic variations in the output, enabling measurement of these effects while maintaining a structured test approach.
Solution Approach 2:
The invention adds another dimension to the test by incorporating frequency modulation and phase modulation aspects alongside traditional amplitude measurements. By using multiple frequencies and analyzing their interactions, the system can detect phase and frequency variations that single-tone tests cannot capture, effectively moving from one-dimensional amplitude measurement to multi-dimensional signal analysis.
Data Source
AI summary
A system is provided to analyze cross-modulation distortion in audio devices, which may include testing with audio frequencies. One or more distortion signals from the audio device may be measured for an amplitude, phase, and or frequency modulation effect. In another embodiment a musical signal may be used as a test signal. Providing additional test signals to the audio device can induce a time varying cross-modulation distortion signal from an output of the audio device. Also utilizing at least one additional filter, filter bank, demodulator and or frequency converter and or frequency multiplier provides extra examination of distortion. Also frequency and or phase response can be measured with the presence of a de-sensing signal and or another signal that induce near slew rate limiting or near overload condition of the device under test.