TI ADC Bandwidth Mismatch Compensation Using Autocorrelation

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Solution Overview

Problem

Current technologies lack an effective method for blindly determining and compensating for bandwidth mismatches in time-interleaved analog-to-digital converters (TI ADCs), which significantly affect the performance of high accuracy and high speed ADCs, especially in achieving the desired Spurious-Free Dynamic Range (SFDR) greater than 70 dB.

Innovation Solution

An apparatus comprising multiple ADC branches with adjustable track-and-hold circuits, sub-ADCs, multiplexers, and a mismatch estimation circuit that calculates and adjusts filter characteristics to determine and compensate for bandwidth mismatches using autocorrelation sequences and cost functions, ensuring matching within 0.1% to 0.25% bandwidth variation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If bandwidth mismatch correction is implemented in time-interleaved ADCs, then Spurious-Free Dynamic Range (SFDR) is improved to greater than 70 dB, but device complexity increases due to the need for additional mismatch estimation and compensation circuits

Engineering Contradiction:

ImproveSFDRVSAvoidmismatch estimation circuit

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The system performs self-diagnosis and self-correction by automatically estimating bandwidth mismatches using autocorrelation sequences and applying compensation through adjustable filter characteristics, eliminating the need for external calibration equipment or manual adjustment

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The invention dynamically adjusts the filter characteristics (bandwidth parameters) of the track-and-hold circuits based on estimated mismatch values to compensate for bandwidth variations between ADC branches, thereby improving SFDR performance

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If blind bandwidth mismatch estimation is performed using autocorrelation sequences, then manufacturing precision is improved by achieving 0.1% to 0.25% bandwidth matching, but measurement precision requirements increase

Engineering Contradiction:

Improvebandwidth matchingVSAvoidautocorrelation estimation

Core Design Contradiction:

Manufacturing precisionVSMeasurement precision

Solution Approach 1:

The system uses autocorrelation sequence estimation to provide feedback information about bandwidth mismatches, which is then used to adjust filter characteristics in a closed-loop manner to achieve precise bandwidth matching

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The mismatch estimation is performed during the calibration phase before normal operation, allowing the system to pre-determine compensation parameters that are then applied during actual signal conversion

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS8094050B2Bandwidth mismatch estimation in time-interleaved analog-to-digital converters

Publication Date: 2012.01.10 TEXAS INSTRUMENTS INC

AI summary

With high speed, high resolution time-interleaved (TI) analog-to-digital converters (ADCs), bandwidth mismatches between the various ADC branches can pose a significant problem. Previously, though, no adequate solution has been found. Here, a method and apparatus are provided that can calculate and compensate for bandwidth mismatches in a TI ADC, enabling a high speed, high resolution TI ADC to be produced.