Analog Predistortion Power Amplifier Using IMD Sweet Spots for WCDMA Applications

This paper presents an analog predistortion power amplifier (PA) using intermodulatoin distortion (IMD) sweet spots to cancel the third and fifth-order intermodulation (IM3 and IM5) components for linearity improvement in wide-band code division multiple access (WCDMA) applications. A third- order predistorter (PD) is used to cancel the IM3 components when the IM5 components are significantly reduced by the IMD5 sweet spots of the PA. For experimental validation, a 30-W PEP LDMOSFET PA is implemented and tested for two-tone and 4- carrier WCDMA signals at 2.14 GHz. The positions of the IMD5 sweet spots are predicted by the mathematical approach using the Ids-Vgs curve and two-tone distortion products. With a third- order PD and the IMD5 sweet spots of the PA the significant IMD suppression and adjacent channel leakage ratio (ACLR) improvements are obtained.