Delta-Sigma Modulator Error Feedback for Zero-Input Noise Suppression
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Solution Overview
Problem
Conventional delta-sigma modulators produce undesirable out-of-band noise when the input signal is zero or very small, leading to limited cycle oscillations and in-band noise due to aliased out-of-band noise.
Innovation Solution
Implement a gravity effect to converge memory elements in the error feedback loop, ensuring the output goes to zero when the input is zero, using a small adjustment to memory elements to maintain performance without introducing significant noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional delta-sigma modulator is used, then high resolution output is achieved, but out-of-band noise is generated when input signal is zero or very small
Solution Approach 1:
The patent applies feedback control by monitoring the output of the delta-sigma modulator and detecting limit cycle oscillations. When limit cycles are detected, the system adjusts the quantizer output or modifies the feedback path to eliminate the oscillations, thereby reducing out-of-band noise while preserving the high resolution output capability during normal operation.
Solution Approach 2:
The system dynamically adjusts its operation mode based on the input signal level. When the input signal is zero or very small, the modulator transitions to a special mode that suppresses limit cycle oscillations. This dynamic adaptation allows the system to maintain high resolution for normal signals while eliminating out-of-band noise for zero or near-zero inputs.
2Object-generated harmful factors
If limit cycle oscillation is prevented by resetting feedback quantity to zero, then out-of-band noise is reduced, but in-band noise performance may be degraded
Solution Approach 1:
The patent applies local quality by selectively applying different processing to different frequency components. The system identifies and suppresses limit cycle oscillations in the out-of-band region while leaving the in-band signal components unchanged. This selective approach ensures out-of-band noise is reduced without degrading in-band noise performance.
Solution Approach 2:
The system introduces an intermediary component (such as a noise detector or spectral analyzer) that monitors the modulator output and distinguishes between limit cycle oscillations and valid signal components. This intermediary enables selective suppression of harmful oscillations while preserving the desired signal and its noise characteristics.
Data Source
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AI summary
Systems and methods according to one or more embodiments are provided for improving noise performance in a delta sigma modulator comprising an adder, quantizer and nth order filter. The adder is operable to receive an input signal and a feedback signal, and output a modified input signal. The quantizer is operable to receive the modified input signal and output a quantized output signal, the quantized output signal having a corresponding quantization error. The nth order filter is operable to receive a quantization error value and generate the feedback signal, the nth order filter comprising a first memory element having a first error value, a second memory element having a second error value, and a gravity component operable to converge the first error value and the second error value when the input signal is approximately zero.