Series-Connected Delta-Sigma Modulator for High SNDR Input Range
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Solution Overview
Problem
Delta-sigma modulators (DSM) face a challenge in maintaining a high signal-to-noise-and-distortion ratio (SNDR) while allowing a large input range, as high-frequency-shaped noises can exceed the quantizer's full scale, leading to clipping errors that degrade SNDR when the input signal is large.
Innovation Solution
A series-connected DSM configuration, comprising a first DSM with aggressive noise-shaping for high SNDR and a second DSM with extended quantization levels to minimize clipping errors, ensuring both high SNDR and large input range by separating quantization and clipping error processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the input signal range of the DSM is increased, then the input range is improved, but the SNDR degrades due to clipping errors
Solution Approach 1:
The patent divides the single DSM into two cascaded DSMs: a first DSM that handles noise shaping for high SNDR, and a second DSM that handles clipping error correction. This segmentation allows each stage to specialize in different error types, resolving the contradiction between input range and SNDR by distributing functionality across multiple components.
Solution Approach 2:
The patent introduces an intermediary error correction mechanism between the two DSMs. The second DSM acts as a mediator that receives the quantized output from the first DSM and corrects clipping errors before final output. This intermediary stage enables the system to maintain high SNDR while accepting larger input signals that would otherwise cause clipping.
2Reliability
If aggressive noise-shaping is applied to achieve high SNDR, then the SNDR is improved, but the clipping error increases leading to SNDR degradation
Solution Approach 1:
The patent converts the harmful clipping error into a correctable artifact by designing the second DSM specifically to detect and correct clipping errors. The aggressive noise-shaping in the first DSM creates high-frequency shaped noises that may clip, but the second DSM treats these clipping errors as correctable disturbances, transforming what would be harmful distortion into a manageable error type that can be recovered.
Solution Approach 2:
The patent implements a feedback mechanism where the quantized output of the first DSM is fed into the second DSM, which monitors for clipping errors and generates correction signals. This feedback loop allows the system to detect when clipping occurs and actively compensate for it, maintaining high SNDR even when aggressive noise-shaping pushes the signal to the quantizer's full scale.
Data Source
AI summary
A series-connected delta-sigma modulator (DSM) comprises a first DSM, configured to receive an input signal, comprising a first loop filter, configured to generate a first processed signal; and a first quantizer, coupled to the first loop filter, configured to generate a first quantized signal, and to feed back the first quantized signal to the first loop filter, wherein the first quantized signal comprises a clipping error smaller than a first predetermined value; and a second DSM, coupled to the first DSM, configured to receive the first quantized signal from the first DSM, comprising a second loop filter, configured to generate a second processed signal; and a second quantizer, coupled to the second loop filter, configured to generate a second quantized signal, and to feed back the second quantized signal to the second loop filter, wherein the second quantized signal comprises a quantization error smaller than a second predetermined value.