A 0.35-μm SiGe WCDMA Direct Conversion Transmitter with DC Offset Compensation for Carrier Leakage Reduction

摘要

A direct conversion transmitter for WCDMA application is presented in this paper. The baseband DC offset voltage of this transmitter is adjustable, such that carrier leakage power at the quadrature modulator output can be minimized. With mis adjustable DC offset voltage, gain control with large dynamic range can be distributed in baseband to implement accurate gain control. An auto-calibration algorithm is also implemented in the baseband filter to adjust its cutoff frequency to 3.2MHz. The current consumption of the transmitter is only 46.4mA under 2.7V power supply and can be further reduced at smaller output power. The measured EVM performance is 1.2% at maximum output power.