Delta-Sigma Modulator Dynamic Feedback for Stable 1-Bit PDM
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Solution Overview
Problem
Existing delta-sigma modulators face challenges in achieving stable operation with high-order loop filters, particularly in handling excessive inputs without oscillation, and require gain scaling methods that increase power consumption and reduce dynamic range.
Innovation Solution
A delta-sigma modulator configuration with a higher-order loop filter and a 1.5-bit quantizer that uses second feedback components to dynamically adjust feedback, eliminating the need for conventional gain scaling and achieving a 1-bit PDM signal with a duty ratio close to 0%-100%, thereby enhancing dynamic range and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional gain scaling methods are used to handle excessive inputs in higher-order delta-sigma modulators, then system stability is improved, but power consumption increases and dynamic range is reduced
Solution Approach 1:
The patent applies dynamics by making the feedback gain adjustable rather than fixed. The feedback gain is dynamically changed based on the input signal level: for normal input levels, a first feedback gain is used, and for excessive input levels, a second feedback gain (different from the first) is applied. This dynamic adjustment allows the system to maintain stability during excessive inputs while avoiding the continuous power consumption overhead of conventional gain scaling methods, thereby resolving the contradiction between stability and power consumption.
2Stability of the object's composition
If conventional gain scaling methods are used to handle excessive inputs, then system stability is improved, but dynamic range is reduced
Solution Approach 1:
The patent employs dynamics by implementing a dynamic feedback gain adjustment mechanism that adapts to different input signal conditions. When the input signal is within the normal range, the system operates with a first feedback gain that maintains wide dynamic range. When excessive input is detected, the system switches to a second feedback gain to ensure stability. This dynamic adaptation resolves the contradiction by preserving dynamic range during normal operation while ensuring stability during excessive inputs.
Solution Approach 2:
The patent applies parameter changes by modifying the feedback gain parameter based on input signal conditions. The feedback gain is changed from a first value (for normal inputs) to a second value (for excessive inputs). This parameter change allows the system to expand its effective dynamic range by adapting to different signal levels, thereby resolving the contradiction between stability and dynamic range.
3Measurement precision
If higher-order loop filters are used to improve noise shaping, then S/N ratio is improved, but system stability deteriorates due to oscillation
Solution Approach 1:
The patent resolves the contradiction between noise shaping performance and system stability by applying dynamics through conditional feedback gain adjustment. Higher-order loop filters are used to achieve superior noise shaping and S/N ratio performance. To prevent oscillation, the system dynamically adjusts the feedback gain: using a first feedback gain during normal operation to maintain stability, and switching to a second feedback gain when excessive inputs are detected that could cause oscillation. This dynamic control enables the system to achieve both high S/N ratio and stability.
Data Source
AI summary
An object is to provide a stable delta-sigma modulator having good microlevel signal reproducibility and capable of outputting a 1-bit PDM signal with a low oversampling ratio of about 64 times at a high duty ratio of 90% or more. The delta-sigma modulator has a higher-order loop filter; a first 1-bit quantizer for making a decision as to the output of the higher-order loop filter; a first feedback component for feeding the first output signal back to the input stage of the higher-order loop filter; a second 1.5-bit quantizer for making a decision as to the output absolute value of an internal stage to be monitored; a second dynamic feedback component for feeding a second output signal back to the input stage of the higher-order loop filter; and an operational unit for producing a 1-bit PDM signal Y by performing operation on the first output signal and second output signal.