Audio Equipment Evaluation for Dynamic Distortion and Phase Modulation
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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 changes in frequency and phase response.
Innovation Solution
The use of filter banks and multiple frequency signals to measure dynamic harmonic and intermodulation distortion, allowing for the detection of phase and frequency modulation effects across varying bias points, enabling a more comprehensive evaluation of audio equipment performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional single-tone tests at fixed bias points are used, then the testing method is simple and equipment requirements are basic, but the measurement precision of time-varying distortion is insufficient
Solution Approach 1:
The patent divides the measurement task into multiple frequency components using filter banks. Instead of measuring distortion at a single frequency, the system segments the spectrum into multiple bands and measures harmonic and intermodulation distortion products in each band separately, enabling time-varying distortion measurement across the entire frequency range.
Solution Approach 2:
The patent transitions from static single-tone tests to dynamic multi-tone testing. By applying multiple simultaneous tones and using a stairstep signal to vary bias points dynamically, the system captures time-varying distortion characteristics that conventional static methods miss, while the filter bank tracks these changes in real-time.
2Measurement precision
If conventional harmonic distortion tests at zero offset are used, then the testing procedure is straightforward, but the measurement cannot detect differential phase and frequency modulation effects
Solution Approach 1:
The patent introduces a stairstep signal as an intermediary that modulates the bias point dynamically. This intermediary signal enables the detection of differential phase and frequency modulation effects by creating controlled variations in operating conditions, allowing the measurement system to capture dynamic distortion characteristics without directly measuring phase and frequency changes.
Solution Approach 2:
The patent employs periodic stairstep signals to modulate the bias point rhythmically. This periodic variation in bias conditions allows the system to detect time-varying distortion, differential phase, and frequency modulation effects by analyzing how the distortion products respond to the periodic bias changes, converting difficult-to-measure dynamic effects into detectable amplitude modulations.
3Measurement precision
If conventional intermodulation distortion tests with two tones are used, then the test setup is relatively simple, but the measurement does not account for dynamic changes across varying bias points
Solution Approach 1:
The patent merges multiple measurement functions into a single integrated system. By combining multi-tone signal generation, dynamic bias modulation via stairstep signals, and filter bank analysis into one cohesive measurement apparatus, the system achieves comprehensive dynamic intermodulation distortion measurement across varying bias points while managing complexity through functional integration.
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. Utilizing at least one additional filter, filter bank, demodulator and or frequency converter and or frequency multiplier provides extra examination of distortion. 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 a device. Another system is provided to analyze modulation index differences between input and output signals for a test signal including modulation.