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Degradation of Alias Rejection in Continuous-Time Delta-Sigma Modulators by Weak Loop-Filter Nonlinearities
, Saravana Manivannan
Published in Institute of Electrical and Electronics Engineers Inc.
2018
Volume: 65
   
Issue: 10
Pages: 3207 - 3215
Abstract
Implicit anti-aliasing is a remarkable property of continuous-time delta-sigma modulators employing a time-invariant loop filter. It turns out that weak nonlinearity of the operational transconductance amplifier (OTA) used in the input integrator, in conjunction with the DAC pulse shape and OTA parasitics can greatly degrade the alias rejection of the modulator. The authors report and analyze this hitherto undiscovered mechanism. The theory is borne out by measurement results from a fourth-order single-bit filtering delta-sigma modulator designed in a 65-nm CMOS process. The alias-rejection of the modulator, which is expected to be about 160dB, is degraded to around 70dB by weak OTA nonlinearity and OTA parasitics. © 2004-2012 IEEE.
About the journal
JournalData powered by TypesetIEEE Transactions on Circuits and Systems I: Regular Papers
PublisherData powered by TypesetInstitute of Electrical and Electronics Engineers Inc.
ISSN15498328
Open AccessNo
Concepts (18)
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    Anti-aliasing
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    Bandpass filters
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    Continuous time systems
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    Delta sigma modulation
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    ELECTRIC FILTERS
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    Filtration
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    MIXER CIRCUITS
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    Mixing
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    Operational amplifiers
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    Aliasing
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    Continuous-time
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    DELTA SIGMA MODULATOR
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    INTEGRATOR
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    OPERATIONAL TRANSCONDUCTANCE AMPLIFIERS (OTA)
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    OVERSAMPLED
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    TIME VARIANT
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    WEAK NONLINEARITY
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    MODULATORS