Interleaved ADC Timing Skew Correction Using Blind Gradient Estimation
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Solution Overview
Problem
Interleaved analog-to-digital converters (ADCs) face timing skew issues due to phase mismatches between branches, which affect high-speed and high-performance operations, necessitating effective estimation and correction methods.
Innovation Solution
A method and system for estimating timing skew using a gradient loop on the output of interleaved ADCs, involving cross-correlation calculations, cost function determination, and gradient-based corrections, allowing for blind estimation without requiring specific input signal properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If multiple interleaved ADCs are used to increase sampling rate, then the sampling rate is improved, but timing skew between branches is introduced
Solution Approach 1:
The patent implements a feedback mechanism where the estimated timing skew is continuously used to correct the sampling instances of interleaved ADC branches. The correction unit adjusts the sampling timing based on the estimated skew, creating a closed-loop system that maintains timing accuracy despite the inherent skew introduced by interleaving multiple ADCs to achieve high sampling rates.
Solution Approach 2:
The patent changes the timing parameter of ADC sampling by estimating the skew between branches and applying corrections. The system dynamically adjusts the sampling instance parameters based on the calculated timing differences, allowing the interleaved ADC system to maintain synchronization while operating at high sampling rates.
2Measurement precision
If timing skew correction is implemented, then timing accuracy is improved, but system complexity increases
Solution Approach 1:
The patent replaces complex hardware-based timing correction mechanisms with a software/digital signal processing approach. By using cross-correlation algorithms and gradient descent optimization in the digital domain, the system achieves timing skew correction without requiring additional physical correction hardware, thereby reducing overall system complexity while maintaining timing accuracy.
Solution Approach 2:
The timing skew correction system is self-calibrating using the input signal itself. The cross-correlation-based estimation method uses the actual signal passing through the ADC branches to automatically determine and correct timing skew, eliminating the need for external calibration equipment or complex manual adjustment mechanisms.
3Adaptability or versatility
If blind timing skew estimation is performed, then adaptability to different input signals is improved, but estimation accuracy may be affected without signal property knowledge
Solution Approach 1:
The patent performs preliminary cross-correlation analysis between ADC branch outputs to establish a baseline understanding of the signal characteristics before proceeding with gradient-based skew estimation. This preliminary action allows the system to adapt to different signal types while maintaining estimation accuracy by preparing the necessary correlation data in advance.
Solution Approach 2:
The patent employs a dynamic gradient descent optimization process that adapts to the specific characteristics of each input signal. The gradient-based estimation method dynamically adjusts the skew correction based on the actual signal properties observed in real-time, allowing the system to maintain high estimation accuracy across different signal types without requiring prior knowledge of signal characteristics.
Data Source
AI summary
A timing skew estimation system is disclosed that includes a plurality of interleaved analog-to-digital converter circuits (ADCs), a timing mismatch estimation unit, and a correction unit. The timing mismatch estimation unit calculates a correlation between each of the plurality of ADCs. Then the timing mismatch estimation unit calculates a cost function for each of the plurality of ADCs, except the reference ADC. The timing mismatch estimation unit further calculates a gradient for each of the plurality of ADCs, except the reference ADC. The timing mismatch estimation unit also continually calculates the timing skew of each of the plurality of ADCs, except the reference ADC, as the sum of an immediately previous estimate of the timing skew of each ADC, except the reference ADC, and a product of a function of the gradient of each of the plurality of ADCs, except the reference ADC, and a step size, The correction unit continually corrects the output of each of the plurality of ADCs, except the reference ADC, based on the estimates of the timing skew of each of the plurality of ADCs, except the reference ADC. Eventually, the timing skew estimation system determines a converged estimate of the timing skew of each of the plurality of ADCs, except the reference ADC. A method of estimating timing skew and timing skew estimation circuitry are also disclosed.