A 0.18μm CMOS fully integrated RFDAC and VGA for WCDMA transmitters

A digital IF to RF converter architecture with an RF VGA targeted for WCDMA transmitters is presented. The RFDAC consists of a 1.5-bits current steering DAC with an embedded semi-digital FIR filter and a mixer with an LC load. The VGA controls the output power in 10dB steps. The prototype is fabricated in 0.18μm CMOS technology and achieves 0dBm output power at 2GHz and 33dB image rejection. The measured rms EVM and ACPR show the system fulfills the standard specifications for the WCDMA. The chip draws 123.9mA from 1.8V supply. The die area is 0.8 × 1.6 mm
²
.