RF DAC Background Error Measurement Using Transparent Dither
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-speed digital to analog converters (DACs) face significant challenges due to static errors and timing skew errors caused by process, voltage, and temperature variations, which degrade the quality of the analog output and deteriorate the Signal-to-Noise-and-Distortion Ratio (SNDR) and spurious free dynamic range (SFDR) performances.
Innovation Solution
A background measurement technique is employed that injects a transparent dither signal into the DAC system, uses an observer analog to digital converter to digitize the output, and performs cross-correlation to extract static and timing skew errors, allowing for efficient correction of mismatches in DAC cells without requiring extensive hardware or calibration time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional calibration methods are used to reduce static and timing skew errors, then measurement precision improves, but device complexity and calibration time increase
Solution Approach 1:
A dither signal is introduced as an intermediary to facilitate error measurement. The dither signal modulates the DAC output, enabling static and timing skew errors to be extracted through cross-correlation without requiring complex calibration hardware or procedures
Solution Approach 2:
The patent replaces complex mechanical/calibration-based error measurement systems with a signal processing approach. By using dither modulation and cross-correlation in the digital domain, the method eliminates the need for physical calibration equipment and procedures
2Manufacturing precision
If extensive calibration procedures are implemented to reduce timing skew errors, then manufacturing precision improves, but productivity decreases
Solution Approach 1:
The error measurement can be performed continuously or periodically without interrupting DAC operation. The dither signal is added to the normal digital input, allowing error extraction to occur alongside regular DAC functionality, eliminating separate calibration steps
Solution Approach 2:
The DAC system performs self-diagnosis by using its own output (modulated by dither) as the measurement signal. The cross-correlation process extracts errors directly from the DAC's own behavior, eliminating the need for external calibration equipment or procedures
3Measurement precision
If high-resolution error measurement is performed to improve SNDR and SFDR, then measurement precision improves, but power consumption increases
Solution Approach 1:
The dither signal serves as a low-power intermediary that enables high-precision error measurement. By modulating the DAC output with a simple periodic or pseudo-random dither sequence, the system can extract detailed error information through cross-correlation without requiring high-power measurement equipment
Solution Approach 2:
The patent replaces power-intensive physical measurement systems with computationally-efficient signal processing. The cross-correlation operation can be performed using simple digital logic or software, consuming minimal power compared to traditional high-resolution measurement hardware
Data Source
AI summary
Digital to analog conversion generates an analog output corresponding to a digital input by controlling unit elements or cells using data bits of the digital input. The unit elements or cells individually make a contribution to the analog output. Due to process, voltage, and temperature variations, the unit elements or cells may have mismatches. The mismatches can degrade the quality of the analog output. To extract the mismatches, a transparent dither can be used. The mismatches can be extracted by observing the analog output, and performing a cross-correlation of the observed output with the dither. Once extracted, the unit elements or cells can be adjusted accordingly to reduce the mismatches.