Digital Filter Gain Updating to Minimize Audio Transients
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Solution Overview
Problem
Existing digital microphone architectures face challenges in minimizing audible transients due to gain changes, which affect performance metrics such as signal-to-noise ratio (SNR) and total harmonic distortion (THD), while maintaining dynamic acoustic overload point (AOP) switching and reducing power consumption.
Innovation Solution
Implementing a filter architecture with a delay line and gain components that adjust their values during normal and transient modes of operation, storing signal history in memory and updating gain values to minimize transients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a stronger low-pass filter with lower cut-off frequency is applied, then signal reconstruction quality is improved, but transient signals are strengthened
Solution Approach 1:
The patent applies preliminary action by pre-scaling the delay line contents with the new gain value before the actual gain change occurs. This preparatory scaling ensures that when the gain change happens, the filter already has the correct scaled values ready, preventing transient signals while maintaining signal reconstruction quality.
Solution Approach 2:
The patent implements dynamics by making the gain value time-varying and adjustable. The filter transitions from a static gain value to a dynamic gain value that can be updated without causing transients, allowing the system to adapt to changing signal conditions while maintaining stability.
2Use of energy by moving object
If gain change is applied in PGA to achieve higher dynamic range, then power consumption is reduced, but audible transient signals are generated
Solution Approach 1:
The patent uses preliminary action by updating the delay line contents with the new gain value before the gain change takes effect. This ensures that the digital filter is already prepared with the correct scaled values, eliminating audible transients while allowing the PGA to switch gain settings for power savings and dynamic range optimization.
Solution Approach 2:
The patent introduces an intermediary mechanism - the delay line content scaling - that mediates between the PGA gain change and the digital filter output. This intermediary scaling operation ensures a smooth transition without generating transients, allowing the system to benefit from both power reduction and audio quality.
3Adaptability or versatility
If gain value is updated in digital filter, then dynamic acoustic overload point switching is achieved, but transients are generated reducing performance
Solution Approach 1:
The patent applies preliminary action by pre-scaling all delay line contents with the new gain value before the gain change occurs. This ensures that when the gain value is updated for dynamic AOP switching, the filter already contains the correctly scaled historical values, preventing transients and maintaining performance reliability.
Solution Approach 2:
The patent implements parameter changes by dynamically updating the gain value stored in the delay line contents. This allows the system to switch between different acoustic overload points by changing the gain parameter, while the preliminary scaling ensures that these parameter changes do not generate harmful transients.
Data Source
AI summary
A filter includes a delay line; at least one gain component coupled to the delay line; and a summer coupled to the delay line, wherein the at least one gain component includes a first value during a normal mode of operation, and wherein the at least one gain component includes a second value during a transient mode of operation.