Time-Interleaved ADC Dynamic Matching for Spurious Tone Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional time-interleaved analog-to-digital converters (ADCs) suffer from limited spectral performance due to mismatch between low-sampling-rate units, leading to spurious tones that result in false positives and false negatives in applications like LiDAR and radar, where high sampling rates and spurious-free dynamic range (SFDR) are crucial for accurate range detection.
Innovation Solution
The proposed solution involves using a slightly larger number of sub-ADCs (N+2) and dynamically selecting them to randomize or spectrally shape their mismatches, thereby improving the SFDR and reducing spurious tones, which are combined using a merge circuit and controlled by a control circuit that selects sub-ADCs based on spectral tones and calibration characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional time-interleaved ADC architecture is used to achieve high sampling rate, then sampling rate is improved, but spectral performance deteriorates due to mismatch between sub-ADC units
Solution Approach 1:
The patent applies dynamic element matching by randomly selecting which sub-ADC units are active during conversion, making the system dynamic rather than static. This randomization transforms the deterministic mismatch pattern into a stochastic process, pushing spurious tones out of the signal band and improving spectral performance while maintaining high sampling rate
Solution Approach 2:
The patent changes the operational parameters of sub-ADC units by dynamically adjusting which units are active based on random selection. This parameter change transforms the fixed mismatch characteristics into variable characteristics, thereby improving spectral performance without sacrificing the high sampling rate achieved through time-interleaving
2Productivity
If more sub-ADC units are added to improve sampling rate, then productivity is improved, but device complexity increases
Solution Approach 1:
The patent uses N+2 sub-ADC units instead of exactly N units, applying partial excess to the number of units. This excessive action provides redundancy that enables dynamic element matching, improving spectral performance while the additional complexity is minimal compared to the benefit gained in spurious-free dynamic range
Data Source
AI summary
Analog-to-digital converters (ADCs) with a high sampling rate and larger spurious-free dynamic range (SFDR) in the spectral domain are used in many applications, including, but not limited to, range finders, meteorology, spectroscopy, and/or coherent medical imaging. Circuit techniques for time-interleaving a set of low-sampling-rate sub-ADCs into a higher sampling-rate ADC with a larger SFDR than existing approaches are described. In one embodiment, the circuit techniques add a small number of additional units or sub-ADCs. This change in architecture enables a dynamic-selection procedure to time-interleave the set of sub-ADCs in such a way that mismatch-related non-idealities of the constituent sub-ADCs are spread in the frequency domain into a noise-like spectral shape in order to prevent the creation of spurious tones, which would otherwise deleteriously impact the SFDR.