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Analysis, Estimation and Compensation of Mismatch Effects in A/D Converters
Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The trend in modern communication systems is to replace as much analog circuits as possible with digital ones, to decrease size, energy consumption and cost. An analog to digital converter (ADC) is the interface between the analog and digital parts. Replacing analog parts, such as mixers, with digital ones requires higher sampling rates. The bottleneck in a digital communication system is often the ADC. Requirements on low power consumption, small chip area and high sample rates are often contradictory to requirements on high accuracy in the manufacturing process.

The traditional way to improve the accuracy is to calibrate the ADC before use. However, calibration is time consuming and costly. Furthermore, the errors usually change during the lifetime of the ADC due to, for instance, temperature variation and aging. This means that the ADC must be recalibrated at regular intervals.

In this thesis, we investigate how the errors in an ADC can be estimated and compensated for while the ADC is used. The estimation must then be done without any special calibration signal. Two different types of errors are discussed in this thesis. The first type of error is static errors in the reference levels, caused by resistor mismatch. Two methods are proposed for estimation and correction of these errors. The most general method requires only that the amplitude distribution is smooth, while the other one requires knowledge of the amplitude distribution of the input signal butgives a little better performance.

The second type of error occurs in time interleaved ADCs, where several ADCs are used in parallel. Due to component mismatch, three different static errors appear: Time errors (static jitter), amplitude offset errors and gain errors. A method for estimation and compensation of these errors is proposed. The method requires basically only that the input signal is band limited to the Nyquist frequency for the system.

Another way to decrease the impact of the mismatch errors in a time interleaved ADC is to randomize the selection of which order the ADCs should be used. This randomization spreads the distortion to a more noise like shape. How the mismatcherrors aect the spectrum of a randomly interleaved ADC is also analyzed in this thesis.

To confirm that the analysis and estimation methods work in practise the methods are evaluated on both simulated data and data from real ADCs.

Place, publisher, year, edition, pages
Linköping: Linköping University , 2003. , 247 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 811
Keyword [en]
A/D converter
National Category
Control Engineering
Identifiers
URN: urn:nbn:se:liu:diva-98170ISBN: 91-7373-621-X (print)OAI: oai:DiVA.org:liu-98170DiVA: diva2:652358
Public defence
2003-05-07, Visionen, Hus B, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Supervisors
Available from: 2013-10-09 Created: 2013-09-30 Last updated: 2013-10-09Bibliographically approved
List of papers
1. Equalization of Time Errors in Time Interleaved ADC System - Part II: Analysis and Examples
Open this publication in new window or tab >>Equalization of Time Errors in Time Interleaved ADC System - Part II: Analysis and Examples
2003 (English)Report (Other academic)
Abstract [en]

In the accompanying paper a method for blind (i.e., no calibration needed) estimation and compensation of the time errors in a time interleaved ADC system was presented. In this paper we evaluate this method. The Cramer-Rao bound is calculated, both for additive noise and random clock jitter. Monte-Carlo simulations have also been done to compare to the CRB. Finally, the estimation method is validated on measurements from areal time interleaved ADC system with 16 ADCs.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2003. 11 p.
Series
LiTH-ISY-R, ISSN 1400-3902 ; 2495
Keyword
A/D conversion, Nonuniform sampling, Equalization, Estimation
National Category
Control Engineering
Identifiers
urn:nbn:se:liu:diva-55912 (URN)LiTH-ISY-R-2495 (ISRN)
Available from: 2010-04-30 Created: 2010-04-30 Last updated: 2014-07-29Bibliographically approved
2. Equalization of Time Errors in Time Interleaved ADC System - Part I: Theory
Open this publication in new window or tab >>Equalization of Time Errors in Time Interleaved ADC System - Part I: Theory
2003 (English)Report (Other academic)
Abstract [en]

To significantly increase the sampling rate of an A/D converter (ADC), a time interleaved ADC system is a good option. The drawback of a time interleaved ADC system is that the ADCs are not exactly identical dueto errors in the manufacturing process. This means that time, gain and offset mismatch errors are introduced in the ADC system. These errors cause distortion in the sampled signal. In this paper we present a method for estimation and compensation of the time mismatch errors. The estimation method requires no knowledge about the input signal except that it should be band limited to the Nyquist frequency for the complete ADC system. This means that the errors can be estimated whilethe ADC is running. The method is also adaptive to slow changes in the time errors.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2003
Series
LiTH-ISY-R, ISSN 1400-3902 ; 2494
Keyword
A/D conversion, Nonuniform sampling, Equalization, Estimation
National Category
Control Engineering
Identifiers
urn:nbn:se:liu:diva-55911 (URN)
Available from: 2010-04-30 Created: 2010-04-30 Last updated: 2013-10-09
3. Blind Adaptive Equalization of Mismatch Errors in Time Interleaved A/D Converter System
Open this publication in new window or tab >>Blind Adaptive Equalization of Mismatch Errors in Time Interleaved A/D Converter System
2003 (English)Report (Other academic)
Abstract [en]

To significantly increase the sampling rate of an AID converter (ADC), a time-interleaved ADC system is a good option. The drawback of a time-interleaved ADC system is that the ADCs are not exactly identical due to errors in the manufacturing process. This means that time, gain, and offset mismatch errors are introduced in the ADC system. These errors cause distortion in the sampled signal. In this paper, we present a method for estimation and compensation of the mismatch errors. The estimation method requires no knowledge about the input signal except that it should be bandlimited to the Nyquist frequency for the complete ADC system. This means that the errors can be estimated while the ADC is running. The method is also adaptive to slow changes in the mismatch errors. The estimation method has been validated with simulations and measurements from a time-interleaved ADC system.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2003. 13 p.
Series
LiTH-ISY-R, ISSN 1400-3902 ; 2486
Keyword
A/D conversion, Nonuniform sampling, Equalization, Estimation
National Category
Control Engineering
Identifiers
urn:nbn:se:liu:diva-55905 (URN)LiTH-ISY-R-2486 (ISRN)
Available from: 2010-04-30 Created: 2010-04-30 Last updated: 2014-07-29Bibliographically approved
4. Analysis of Mismatch Effects in Randomly Interleaved A/D Converter System
Open this publication in new window or tab >>Analysis of Mismatch Effects in Randomly Interleaved A/D Converter System
2003 (English)Report (Other academic)
Abstract [en]

To significantly increase the sampling rate of an A/D converter (ADC), a time interleaved ADC system is a good option. The drawback of a time interleaved ADC system is that the ADCs are not exactly identical due to errors in the manufacturing process. This means that time, gain and offset mismatch errors are introduced in the ADC system. These errors cause non harmonic distortion in the sampled signal. One way to decrease the impact of the mismatch errors is to spread the distortion over a wider frequency range by randomizing the order in which the ADCs are used in the interleaved structure. In this paper we analyze how the spectrum is affected by mismatch errors in a randomly interleaved ADC system. We also discuss how the mismatch errors can be estimated.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2003. 14 p.
Series
LiTH-ISY-R, ISSN 1400-3902 ; 2496
Keyword
A/D conversion, Nonuniform sampling, Random sampling
National Category
Control Engineering
Identifiers
urn:nbn:se:liu:diva-55913 (URN)LiTH-ISY-R-2496 (ISRN)
Available from: 2010-04-30 Created: 2010-04-30 Last updated: 2014-07-29Bibliographically approved

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