Delta-Sigma Audio Compression Circuit for Lower Bit Transitions
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Solution Overview
Problem
Existing digital microphone systems face challenges in efficiently communicating digital audio signals over buses due to high bit rates and frequent bit changes, which can lead to decreased communication throughput and increased power consumption.
Innovation Solution
A digital compression circuit that compresses uncompressed digital signals into fewer quantization levels by analyzing transition statistics between consecutive samples, reducing the number of bits required for transmission while maintaining signal quality through lossless compression or minimizing degradation outside human hearing ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If numerous quantization levels are used to represent the digital output signal with sufficient quality, then the audio signal quality is improved, but the number of digital bits required increases, causing communication throughput to decrease
Solution Approach 1:
The patent changes the parameter of quantization levels by using a variable number of quantization levels based on the signal characteristics. When the signal has low activity (few transitions), fewer quantization levels are used, reducing the bit rate. When the signal has high activity, more quantization levels are used to maintain quality. This dynamic parameter adjustment resolves the contradiction between signal quality and communication throughput.
Solution Approach 2:
The patent implements a dynamic quantization system where the number of quantization levels is adjusted in real-time based on the activity of the input signal. The system transitions between different quantization modes (e.g., 1-bit, 2-bit, 3-bit, 4-bit) depending on the signal characteristics, making the system adaptable rather than static. This dynamic approach allows the system to maintain high audio quality when needed while reducing bit rate during low-activity periods.
2Measurement precision
If numerous quantization levels are used to represent the digital output signal, then the audio signal quality is improved, but the number of bits in digital codes increases, causing power consumption to increase
Solution Approach 1:
The patent dynamically changes the number of quantization levels based on signal activity, reducing the bit width from potentially 4 bits down to 1 bit when appropriate. This parameter adjustment directly reduces the power consumption of the digital-to-analog converter and other downstream components that process the digital signal, while maintaining audio quality when high bit depth is actually needed.
3Measurement precision
If bits change frequently in the digital signal, then the digital signal can represent audio variations accurately, but communication throughput decreases and power consumption increases
Solution Approach 1:
The patent implements dynamic quantization where the system adapts its behavior based on signal activity. During periods of low signal activity (few transitions), the system uses fewer quantization levels, reducing bit transitions and improving communication throughput. During high-activity periods, the system increases quantization levels to maintain accurate representation, thus dynamically balancing accuracy and throughput.
Data Source
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Figure 3A~3B
AI summary
A system may include a delta-sigma analog-to-digital converter and a digital compression circuit. The delta-sigma analog-to-digital converter may include a loop filter having a loop filter input configured to receive an input signal and generate an intermediate signal responsive to the input signal, a multi-bit quantizer configured to quantize the intermediate signal into an uncompressed digital output signal, and a feedback digital-to-analog converter having a feedback output configured to generate a feedback output signal responsive to the uncompressed digital output signal in order to combine the input signal and the feedback output signal at the loop filter input. The digital compression circuit may be configured to receive the uncompressed digital output signal and compress the uncompressed digital output signal into a compressed digital output signal having fewer quantization levels than that of the uncompressed digital output signal.