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 language | English (US) |
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Article number | 4479884 |
Pages (from-to) | 1059-1068 |
Number of pages | 10 |
Journal | IEEE Transactions on Microwave Theory and Techniques |
Volume | 56 |
Issue number | 5 |
DOIs | |
State | Published - May 2008 |
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