Design of Predistorter Using Measured Nonlinear Characteristics of Power Amplifier with Memory Effect

This paper describes a method to design a predistorter (PD) for a power amplifier (PA) with a memory effect by using nonlinear parameters extracted from measured intermodulation distortion (IMD) for a GaN-FET amplifier. To improve the computational efficiency, the updating of a cancellation signal is provided by an iterative algorithm. It is confirmed that the proposed algorithm attains computational intensity lower than half of a memory polynomial. A computer simulation has clarified that the PD improves the adjacent channel leakage power ratio (ACLR) of OFDM signals with several hundred subcarriers corresponding to 4G mobile radio communications. It has been confirmed that a fifth-order PD is effective up to a higher power level. The improvement of error vector magnitude (EVM) by the PD is also simulated for OFDM signals of which the subcarrier channels are modulated by 16 QAM.