A CMOS Power Amplifier With a Built-In RF Predistorter for Handset Applications

A CMOS power amplifier (PA) with a built-in RF predistorter is proposed to improve the predistortion system efficiency, especially for handset applications. To eliminate the power consumption of an external predistorter and digital-to-analog converters in the control signal paths, the driver stage of the proposed PA has gain and phase control abilities according to two digital control words. This compensates for the distortions of the PA with envelope-dependent gain and phase control. It is implemented in a 0.18-μm RF CMOS process. The measurement results show 8.7 dB of gain control range and 49.4° of phase control range, which can compensate for the distortions of the designed PA. Using a WCDMA modulated signal, the PA improves its linear output power from 27.2 to 29.1 dBm and its linear efficiency from 34.8% to 41.1% by RF predistortion.