DAC Calibration With Error DACs to Break Current Source Error Accumulation
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Solution Overview
Problem
Digital-to-analog converters (DACs) in wireless communication systems face significant errors due to accumulation of individual errors from current sources, leading to reduced accuracy and performance.
Innovation Solution
The implementation of a DAC system with multiple current sources, calibration DACs, a reference current source, and two error DACs that work in a ping-pong fashion to dynamically adjust and compensate for errors, breaking the error accumulation by using a current mirror and error DACs to calibrate each current source sequentially.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional DAC calibration is used, then the DAC system can operate, but error accumulation from multiple current sources reduces conversion accuracy
Solution Approach 1:
The patent implements feedback by using error DACs to measure and compensate for calibration errors. The error DACs detect the difference between the actual current output and the expected current output, then feed back correction signals to eliminate the accumulated errors from multiple current sources, thereby improving conversion accuracy.
Solution Approach 2:
The patent introduces error DACs as intermediary components between the current sources and the output. These error DACs act as mediators that isolate and compensate for errors introduced by individual current sources, preventing error accumulation and improving overall system reliability and accuracy.
2Measurement precision
If multiple calibration DACs are used to compensate for each current source, then accuracy improves, but device complexity increases
Solution Approach 1:
The patent merges multiple calibration functions into a unified calibration architecture using error DACs. Instead of implementing separate complex calibration circuits for each current source, the error DACs consolidate the calibration function by measuring and compensating errors from all current sources through a unified feedback mechanism, thereby reducing overall device complexity while maintaining high accuracy.
Solution Approach 2:
The error DACs serve multiple functions: they calibrate multiple current sources, measure errors, and provide compensation signals. This multi-functionality eliminates the need for separate dedicated calibration circuits for each current source, reducing device complexity while achieving comprehensive calibration coverage.
3Measurement precision
If sequential calibration of current sources is implemented, then error accumulation is reduced, but calibration time increases
Solution Approach 1:
The patent maintains continuity of useful action during calibration by using error DACs that can continuously or periodically compensate for errors without requiring complete system shutdown or lengthy recalibration procedures. The feedback mechanism allows for ongoing error correction, reducing the effective calibration time while maintaining high precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces error accumulation, improving the accuracy of digital-to-analog conversion and enhancing the signal-to-noise-plus-distortion ratio (SNDR) by four times compared to conventional methods, allowing for smaller calibration DACs and a more efficient DAC system.
Implementation Method 1
a current mirror having a first branch selectively coupled to the plurality of current sources, wherein a second branch of the current mirror is coupled to the reference current source
Data Source
AI summary
Certain aspects of the present disclosure provide a digital-to-analog converter (DAC) system. The DAC system generally includes a plurality of current sources, a plurality of calibration DACs, each coupled to a respective one of the plurality of current sources, a reference current source, and a current mirror having a first branch selectively coupled to the plurality of current sources, wherein a second branch of the current mirror is coupled to the reference current source. The DAC system also includes a first error DAC selectively coupled to the first branch and the second branch of the current mirror, and a second error DAC selectively coupled to the first branch and the second branch of the current mirror.