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Power amplifiers (PAs) are inherently nonlinear devices and are used in virtually all communications systems. Digital baseband predistortion is a highly cost effective way to lin earize the PAs, but most existing architectures ass ume that the PA has a memory less nonlinearity. For wider bandwidth applications such as WCDMA, PA memory effects can no longer be ignored, and memoryless predistortion has limited effectiveness. In tHis paper, we model the PA as a Wiener system and construct a Hammerstein predistorter, obtained using an indirect learning architecture. Linearization per formance is demonstrated on a 3-carrier UMTS signal. 1.. INTRODUCTIONPower amplifiers �rAs) are indispensable components in a communication system and are inherently nonlinear. It is.well known that there is an approximate inverse relationship between the PA efficiency and its linearity. Hence, nonlinear PAs are desirable from an efficiency point of view. The price paid for higher efficiency is that nonlinearity causes spec tral regrowth (broadening) which leads to adjacent channel interference. It also causes in-band distortion which de grades the bit error rate (BER) performance . Newer trans 0-7803-7402-9/02/$17.00

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