Sigma-Delta Modulator Switching for Artifact-Free Digital Microphones
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Solution Overview
Problem
Existing digital microphones face challenges in dynamically changing signal processing parameters without causing audible artifacts, particularly during transitions between operational modes.
Innovation Solution
Implementing a state detection and control component that monitors the output of integrators in a digital microphone, allowing parameter adjustments only when the integrator is at a mean value or within threshold limits to minimize audible transients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If parameter adjustments are made in sigma-delta modulators during operational mode transitions, then adaptability and performance optimization are improved, but audible artifacts and noise are generated
Solution Approach 1:
The system performs preliminary actions by pre-charging capacitor elements to anticipated voltage levels before switching events occur. The control circuit predicts upcoming mode transitions and prepares the integrator capacitors in advance, ensuring they are ready to maintain signal continuity without generating audible artifacts during the actual transition.
Solution Approach 2:
The patent introduces control circuit elements (switches and capacitors) as intermediaries between the signal path and the mode transition event. These intermediary components buffer the transition by providing alternative signal paths and maintaining voltage levels, thereby preventing direct disruption to the audio signal during parameter changes.
2Measurement precision
If clock frequency is changed to optimize microphone performance, then signal-to-noise ratio is improved, but power consumption increases
Solution Approach 1:
The system dynamically adjusts the clock frequency of the sigma-delta modulator based on operational requirements. The control circuit can switch between different clock frequencies to optimize the balance between signal-to-noise ratio and power consumption, allowing the microphone to adapt its performance characteristics to different usage scenarios.
Solution Approach 2:
The patent implements parameter changes by modifying the clock frequency and other operational parameters of the sigma-delta modulator. The control circuit monitors signal conditions and adjusts parameters such as sampling rate and integrator capacitance to maintain optimal performance while managing power consumption efficiently.
3Adaptability or versatility
If seamless switching between operational modes is implemented, then adaptability is improved, but device complexity increases
Solution Approach 1:
The control circuit is designed with multi-functionality to handle various operational mode transitions using a unified control architecture. The same control elements (switches, capacitors, and logic circuits) serve multiple purposes across different switching scenarios, reducing the need for separate dedicated circuits for each mode transition and thereby limiting the increase in overall device complexity.
4Measurement precision
If integrator output is monitored for state detection, then switching precision is improved, but device complexity increases
Solution Approach 1:
The integrator output naturally provides the state information needed for switching detection through its voltage level. The control circuit utilizes this existing signal without requiring additional complex sensing mechanisms, as the integrator's own output state serves as the detection criterion for determining when to execute mode transitions.
Data Source
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Figure 1C
AI summary
A digital microphone includes at least one integrator; a state detection and parameter control component directly coupled to an output of the integrator; and a signal processing component coupled to an output of the state detection and parameter control component, wherein a parameter of the signal processing component includes a first value in a first operational mode and a second value in a second operational mode different from the first operational mode.