Progress In Electromagnetics Research C, Vol. 3, 183–194, 2008 MODELING AND COMPENSATING MEMORY EFFECT IN HIGH POWER AMPLIFIER FOR OFDM SYSTEMS H. Karkhaneh, A. Ghorbani, and H. Amindavar Department of Electrical Engineering Amirkabir University of Technology Hafez Avenue, Tehran, Iran Abstract—This paper is concerned with a new time-domain modeling topology for signals which is applied to OFDM systems. This model is a more accurate based on Wiener approach. Also the memory eﬀect will be shown using two-tone intermodulation distortion (IMD) measurement with diﬀerent tone frequency spacing and power levels. Next adaptive predistorter to counterbalance the AM/AM and AM/PM nonlinear eﬀects of the transmitter power ampliﬁer is proposed by Hammerstein approach. Finally we consider the eﬀectiveness of proposed method on performance of OFDM signal as the wideband system by reduction of distortion. It is conﬁrmed by computer simulation that proposed approach produces a faster convergence speed than the previous adaptive predistortion technique. 1. INTRODUCTION Orthogonal frequency division multiplexing (OFDM) is currently under signiﬁcant investigation due to a high spectral eﬃciency and immunity to multipath fading and impulse noise. Usage of an appropriate guard interval in OFDM can easily prevent intersymbol interference (ISI) and interchannel interference (ICI), whereas powerful equalization techniques are required for single carrier modulation. However, OFDM-based systems are subject to be signiﬁcantly sensitive to nonlinear distortion, usually caused by a high power ampliﬁer [1–3]. High RF power ampliﬁer characterization and modeling has been a subject of study over the last few years. This is mainly driven by the need of a precise behavioral model, which represents the nonlinearity of the high power ampliﬁers (HPAs) and linearizers. The power ampliﬁer is often represented by nonlinear amplitude (AM/AM) and phase (AM/PM) functions in either polar or quadrate form [4–6]. These measurement-based empirical models provide a