Abstract: A sigma--delta (Σ Δ) DAC with channel filtering for multi-standard wireless transmitters used in the software-defined-radio (SDR) system is presented. The conversion frequency, transfer function of the digital filter and the Σ Δ modulator, word-length of the IDAC and cut-off frequency of the analog reconstruction filter can be digitally programmed to satisfy specifications of WCDMA, TD-SCDMA and GSM standards. The Σ Δ DAC fabricated in SMIC 0.13-μm CMOS process occupies a die area of 0.72 mm², while consuming 5.52/4.82/3.04 mW in WCDMA/TD-SCDMA/GSM mode from a single 1.2-V supply voltage. The measured SFDR is 62.8/60.1/75.5 dB for WCDMA/TD-SCDMA/GSM mode, respectively.

Key words: Σ Δ digital-to-analog converter