Analog-to-digital converter using dither and method for converti

Details Analog-to-digital converter using dither and method for converti Analog-to-digital converter using dither and method for converti

1997-10-06

1999-03-30

Williams, Howard L.

Coded data generation or conversion

Analog to or from digital conversion

Increasing converter resolution

341143, H03M 120

Patent

active

058894829

ABSTRACT:
An analog-to-digital converter (100) has a first path (110) with a first sigma-delta modulator (114) which transforms an analog input signal X.sub.0 (111') from an input terminal (101) to a digital output signal Y.sub.0 at an output terminal (102). In a second path (120), a digital dither signal D (121') is combined with a digital intermediate signal Z.sub.0 (115') from the first modulator (114) and digitally processed by a second sigma-delta modulator (124) to an intermediate signal Y.sub.1 (125') Y.sub.1 is fed to the first modulator (114) and to the output terminal (102) with opposite sign ("+" and "-", respectively). Thereby, multipliers (133 and 127) attenuate Y.sub.1. The dither signal D (121') is used substantially only within the converter (100), and is substantially canceled before the output terminal (102). This features preserve a high SNR of the converter (100) and low spectral tones in output signal Y.sub.0.

REFERENCES:
patent: 4968987 (1990-11-01), Naka et al.
patent: 5144308 (1992-09-01), Norsworthy
patent: 5323157 (1994-06-01), Ledzius et al.
patent: 5483238 (1996-01-01), Norsworthy
Franca, J. E., Tsividis, Y, "Design of Analog-Digital VLSI Circuits for Telecommunications and Signal Processing", Second Edition, Prentice Hall, Englewood cliffs, 1994, chapter 10 Delta-Sigma Data Converters by Temes, G. C., on pp. 317-339;.
Norsworthy, S. R., Schreier, R., Temes, G. C.: "Delta-Sigma Data Converters", IEEE Press, New York, 1997, ISBN 0-7803-1045-4;.
Proakis, J. G., Manolakis, D. G., "Digital Signal Processing", Third Edition, Prentice Hall, Englewood Cliffs, 1996, chapter 9.2. Analog-to-Digital Conversion, on pp. 748-762, and chapter 3.1. Z-Transform, on pp. 151-160.

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