Abstract

A noise-shaped direct digital IF to RF (DIF2RF) DAC with embedded upconverter mixer is presented. The digital IF signal is noise shaped by a bandpass Σ-Δ modulator with 1-bit IF output followed by a semidigital finite impulse response (FIR) filter. The current mode FIR filter combines scaled values of the local oscillator (LO) signal for performing reconstruction filtering and upconversion in a single module. The DIF2RF design modulates the digital IF signal with a digital LO signal. This topology eliminates the transconductance nonlinearity of conventional mixers and is inherently linear due to single-bit digital IF input. The presented architecture reduces clock jitter sensitivity of 1-bit DACs by masking IF clock transitions with LO signals. A prototype of the DIF2RF DAC is designed and fabricated in a five-layer metal 0.25-μm digital CMOS process. The architecture can be used in low-power software-defined digital-IF transmitters. The DIF2RF DAC consumes 49 mA from a 2.5-V supply, achieving -64.7-dBc third-order intermodulation at 1.03 GHz with a spurious-free dynamic range of 72 dB in a 15-MHz bandwidth.

Original languageEnglish (US)
Article number4479884
Pages (from-to)1059-1068
Number of pages10
JournalIEEE Transactions on Microwave Theory and Techniques
Volume56
Issue number5
DOIs
StatePublished - May 1 2008

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Keywords

  • CMOS integrated circuits (ICs)
  • Clock jitter
  • Digital-to-analog conversion
  • Mixers
  • Semidigital filtering
  • Sigma-delta modulation
  • Transmitters

ASJC Scopus subject areas

  • Radiation
  • Condensed Matter Physics
  • Electrical and Electronic Engineering

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