Multi-DAC Summation for Speed-Accuracy Tradeoffs
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Solution Overview
Problem
Existing digital to analog conversion techniques face inaccuracies due to current source mismatches and require hardware filters to suppress harmonic content, limiting their efficiency and accuracy.
Innovation Solution
The use of variable output signal magnitude sources, such as variable current or voltage sources, which can be individually set and combined to form the analog signal, allowing for precise adjustment and compensation of mismatches, and optionally paired with a switching element and a semi-digital FIR filter for enhanced accuracy and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If current steering Nyquist DAC is used with binary weighted current sources, then high-speed conversion is achieved, but output signal inaccuracy occurs due to mismatch of weighted current sources
Solution Approach 1:
The patent segments the current sources into multiple groups (first group of current sources and second group of current sources) with different weighting schemes. The first group uses binary weighted current sources for high-speed conversion, while the second group uses equal current sources for accuracy. This segmentation allows each group to optimize for its specific function, resolving the contradiction between speed and accuracy.
Solution Approach 2:
The patent changes the parameters of current sources by providing different weighting configurations to different groups. The first group has current sources with binary weights (1, 2, 4, 8...) optimized for speed, while the second group has equal weights optimized for accuracy. This parameter differentiation allows the system to achieve both high-speed conversion and accurate output signaling.
2Measurement precision
If hardware filter is added to suppress harmonic content, then output signal accuracy is improved, but device complexity increases
Solution Approach 1:
The patent replaces the mechanical hardware filter with a digital filtering approach. Instead of adding physical filter components to the analog output stage, the invention uses digital signal processing techniques to suppress harmonic content. This substitution reduces device complexity while maintaining or improving output signal accuracy.
Solution Approach 2:
The patent introduces an intermediary digital processing stage between the digital input and analog output that performs filtering functions. This intermediary layer handles harmonic suppression through digital means, avoiding the need for complex hardware filters in the analog domain while still achieving the desired signal accuracy.
3Measurement precision
If segmented NYQUIST DAC is used with DEM unit, then mismatch errors are reduced, but device complexity increases due to additional DEM unit
Solution Approach 1:
The patent merges the functions of multiple current source groups into a unified output structure. The first group of binary weighted current sources and the second group of equal current sources are combined in the output stage, allowing their complementary strengths to work together. This merging achieves mismatch error reduction without requiring separate complex DEM units for each group.
Solution Approach 2:
The patent creates a universal current source architecture where the same output summation node handles both binary weighted currents and equal currents. This multi-functional approach allows the system to achieve dynamic element matching benefits for both groups simultaneously, reducing mismatch errors without duplicating DEM unit complexity.
Data Source
AI summary
A method for converting a digital signal to an analog signal, said method including a plurality of signal sources, preferably current sources, one or more of said signal sources being variable output signal magnitude sources, said method including the steps of setting the output signal magnitudes of the one or more variable output signal magnitude sources by individual setting signals being input signals for said respective variable output signal magnitude sources, wherein said conversion is adaptable on a per signal basis in response to needs concerning bandwidth and/or accuracy for achieving a trade-off between sample-rate and resolution of said conversion.