Multi-Path ADC Switching at Zero Crossings to Cut Audio Artifacts
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Solution Overview
Problem
Existing multipath analog-to-digital converters (ADCs) and analog front ends (AFEs) face challenges in smooth transitioning between multiple paths, leading to undesirable signal artifacts, especially in audio applications, and do not scale well to integrated circuit levels.
Innovation Solution
A signal processing system with a controller managing two processing paths, one with lower gain and higher noise floor, and another with higher gain and lower noise floor, where transitions are blended during or near zero cross points of the analog input signal, and predictive methodologies are used to anticipate threshold crossings for smooth path switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If switching between multiple processing paths is implemented to optimize signal processing, then dynamic range and noise performance are improved, but signal artifacts occur during path transitions
Solution Approach 1:
The system performs preliminary actions by detecting threshold crossings and predicting zero-crossing points before the actual path switch occurs. The controller monitors the analog input signal and anticipates the optimal switching moment, preparing the transition in advance to minimize artifacts.
Solution Approach 2:
The patent introduces an intermediary blending mechanism that smoothly transitions between processing paths. Instead of direct switching, the system uses intermediate blending during zero-crossing points to bridge the gap between different gain configurations, eliminating abrupt transitions and associated artifacts.
2Speed
If direct switching between processing paths is used, then transition speed is improved, but signal continuity deteriorates
Solution Approach 1:
The system employs periodic action by utilizing zero-crossing points of the analog input signal as predetermined moments for path transitions. These periodic opportunities provide natural, predictable intervals for switching that maintain signal continuity while enabling relatively fast transitions.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the gain parameter of the processing path based on the signal amplitude. The controller switches between high-gain and low-gain configurations according to whether the signal is below or above a threshold, optimizing performance while maintaining continuity.
3Reliability
If separate optimization for each signal type is implemented, then noise performance is improved, but system complexity increases
Solution Approach 1:
The patent applies universality by designing a single processing system that can handle both small and large amplitude signals through multiple paths. The high-gain path optimizes for small signals while the low-gain path handles large signals, with a controller that universally manages both configurations based on signal conditions.
Solution Approach 2:
The system segments the signal processing function into multiple dedicated paths: a high-gain path for small amplitude signals and a low-gain path for large amplitude signals. Each segment is optimized for its specific signal type, and the controller dynamically selects the appropriate segment based on the current signal level.
Data Source
AI summary
A processing path may include a controller and a plurality of processing paths including a first processing path and a second processing path. The first path may be configured to generate a first digital signal based on an analog input signal and the second path may be configured to generate a second digital signal based on the analog input signal, wherein the first path has a lower gain and a higher noise floor than the second path. The controller may be configured to determine that a transition between the first path and the second path needs to occur based on the analog input signal crossing a threshold or a prediction that the input signal will cross the threshold and in response to determining the transition between the first path and the second path needs to occur, blend the transition during or near zero cross points of the analog input signal.