ADC Reference Path Reconfiguration for Mismatch Distortion Reduction
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Solution Overview
Problem
Data conversion circuits, such as ADCs, suffer from harmonic distortion due to element mismatch, leading to intermodulation distortion products that can cause false targets in radar systems and other applications, which existing dynamic element matching techniques fail to fully address.
Innovation Solution
The introduction of dither into the reference path of a sigma-delta ADC through comparator reference swapping, which randomizes quantization error and reduces deterministic cyclical effects, thereby mitigating distortion and improving spurious-free dynamic range without affecting die area, excess loop delay, or increasing noise generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dynamic element matching techniques are used to address element mismatch in DAC current sources, then harmonic distortion is reduced, but device complexity increases and manufacturing precision requirements are not fully met
Solution Approach 1:
The patent implements dynamic reference signal routing where the reference signal connections to comparators are randomly swapped during operation. This dynamic reconfiguration randomizes the quantization error and reduces deterministic cyclical distortion effects without requiring additional hardware components, thereby improving ADC accuracy while maintaining simple circuit architecture.
Solution Approach 2:
The patent changes the temporal parameter of reference signal assignment by introducing random swapping of reference signal connections to different comparators over time. This parameter change transforms the static reference assignment into a dynamic one, which randomizes quantization error and reduces harmonic distortion without adding complex circuitry.
2Object-generated harmful factors
If element mismatch in DAC current sources is addressed using conventional techniques, then some distortion is reduced, but intermodulation distortion products causing false targets in radar systems persist
Solution Approach 1:
The patent converts the harmful deterministic cyclical quantization error into a beneficial randomized error pattern by implementing random swapping of reference signal connections. This transformation changes the nature of quantization error from correlated and deterministic to uncorrelated and random, which reduces intermodulation distortion products and false targets in radar applications while maintaining acceptable quantization accuracy.
3Measurement precision
If reference path reconfiguration with random swapping is implemented, then harmonic distortion and intermodulation distortion products are reduced, but signal-to-noise ratio may be affected
Solution Approach 1:
The patent implements partial reference swapping where only some comparators have their reference signals randomly swapped rather than all comparators. This partial action allows the system to achieve distortion reduction benefits while minimizing the impact on signal-to-noise ratio, as the degree of swapping can be controlled to balance distortion performance and noise performance.
Data Source
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AI summary
An analog-to-digital converter (ADC) and a method are disclosed. The ADC has a quantizer. The quantizer comprises a linear-feedback shift register (LFSR), a decoder configured to provide a plurality of switch control signals at a plurality of decoder outputs, respectively, the plurality of switch control signals responsive to a LFSR value of the LFSR output; an electrical reference, the electrical reference having a plurality of reference outputs, the electrical reference configured to provide a plurality of reference levels at the plurality of reference outputs, respectively; a first switch providing a first switch output and a second switch output; and a comparator, the comparator having a signal input, a first reference input, and a second reference input, the first reference input connected to the first switch output, and the second reference input connected to the second switch output.