DocumentCode :
1358660
Title :
Design Constraints for Image-Reject Frequency-Translating \\Delta \\Sigma Modulators
Author :
Chopp, Philip M. ; Hamoui, Anas A.
Author_Institution :
Dept. of Electr. & Comput. Eng., McGill Univ., Montreal, QC, Canada
Volume :
56
Issue :
12
fYear :
2009
Firstpage :
896
Lastpage :
900
Abstract :
This brief derives design constraints for bandpass ΔΣ modulators that use mixers to perform frequency downconversion inside their ΔΣ loop. Such systems, which are referred to as frequency-translating ΔΣ modulators, facilitate direct analog-to-digital conversion (ADC) of high-frequency signals that cannot adequately be processed using classical bandpass ΔΣ modulator architectures. The derived constraints are required for the correct design of frequency-translating ΔΣ modulators: 1) The sampling constraints maintain the stability of the ΔΣ feedback loop and prevent the mixing of the undesired signal content into the input-signal band, thereby ensuring that the time-varying behavior of the mixers does not affect the ADC resolution; and 2) the noise- shaping constraints minimize performance loss during the recombination of the in-phase and quadrature feedback paths. This brief analyzes frequency-translating ΔΣ modulators that are designed with image-reject (quadrature) mixing and that are implemented using continuous- or discrete-time lowpass or complex-bandpass inner-loop ΔΣ modulators. Thus, the derived constraints offer a valuable reference for the design of image-reject frequency-translating ΔΣ ADCs.
Keywords :
analogue-digital conversion; delta-sigma modulation; analog-to-digital conversion; classical bandpass ΔΣ modulator architectures; complex-bandpass inner-loop modulators; discrete-time lowpass modulators; feedback loop; image-reject frequency-translating ΔΣ modulators; noise-shaping constraints; Analog-to-digital (A/D) conversion; bandpass; frequency translation; sigma–delta ($DeltaSigma$) modulation;
fLanguage :
English
Journal_Title :
Circuits and Systems II: Express Briefs, IEEE Transactions on
Publisher :
ieee
ISSN :
1549-7747
Type :
jour
DOI :
10.1109/TCSII.2009.2035266
Filename :
5353863
Link To Document :
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