Parallel Sigma-Delta Signal Conversion for Idle Tone Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional digital and analog noise shapers in microphones and analog-to-digital converters experience interference issues, known as idle tones, which can lead to a degraded signal-to-noise ratio, especially for low input signals and high loads, and are inadequate for generating 1-bit output streams.
Innovation Solution
A method and device that involve adding and subtracting a dither signal to and from an input signal, followed by sigma delta conversions and combination of the resulting signals to mitigate idle tones, utilizing a combination of adders, subtractors, and sigma delta converters to generate a digital output signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional digital noise shaper or analog noise shaper is used, then the signal can be converted to a digital output, but idle tones and interference signals occur that degrade the signal-to-noise ratio
Solution Approach 1:
The patent divides the single conversion path into two parallel sigma-delta conversion paths. Each path processes the input signal independently with a dither signal, and the results are combined. This segmentation allows the idle tones from each path to be distributed and reduced when combined, resolving the contradiction between achieving digital conversion and avoiding idle tone interference.
Solution Approach 2:
The dither signal is added to the input signal before the sigma-delta conversion process in both parallel paths. This preliminary action of adding dither noise before conversion prevents the generation of strong idle tones during the quantization process, thereby improving the signal-to-noise ratio without requiring post-processing to remove interference.
2Measurement precision
If a dither signal is added to improve signal-to-noise ratio in conventional approaches, then noise is reduced in specific frequency ranges, but the conventional approaches are inadequate for generating 1-bit output streams and may impede the signal-to-noise ratio
Solution Approach 1:
The patent segments the conversion process into two parallel 1-bit sigma-delta converters, each producing a 1-bit output stream. By combining these two segmented 1-bit streams, the system achieves improved signal-to-noise ratio while maintaining 1-bit output capability, resolving the contradiction between dither-based noise reduction and 1-bit output generation.
Solution Approach 2:
The patent merges the outputs of two parallel sigma-delta converters to generate the final 1-bit output stream. This combining operation integrates the benefits of dither-based noise shaping from both paths while maintaining the 1-bit output format requirement, thereby achieving both improved signal-to-noise ratio and proper 1-bit stream generation.
Data Source
AI summary
In accordance with an embodiment, a method includes adding a dither signal to a first signal to generate a second signal, subtracting the dither signal from the first signal or subtracting the first signal from the dither signal to generate a third signal, performing a first sigma delta conversion of the second signal to a digital fourth signal, performing a second signal delta conversion of the third signal to a digital fifth signal, combining the digital fourth signal and the digital fifth signal to form a digital sixth signal.