Rui J. P. de Figueiredo and Byung Moo Lee,
Laboratory for Intelligent Signal Processing and Communications, University of California, Irvine
SYNCHROINFO JOURNAL. Volume 8, Number 1 (2022). P. 2-6.
Orthogonal Frequency Division Multiplexing (OFDM) has several desirable attributes which makes it a prime candidate for a number of emerging wireless communication standards. However, one of the major problems posed by OFDM is its high Peak-to-Average-Power ratio (PAPR), which seriously limits the power efficiency of the High Power Amplifier (HPA) because of the nonlinear distortion resulting from high PAPR. The present paper presents a new mixed computational/analytical approach for compensation of this nonlinear distortion for the case in which the HPA is a Traveling Wave Tube Amplifier (TWTA) with time-varying characteristic. TWTAs are used in wireless communication systems when high transmission power is required as in the case of the digital satellite channel. Compared to previous pre-distorter techniques based on LUT (Look-Up Table) or adaptive schemes, our approach relies on the analytical inversion of the Saleh TWTA model in combination with a nonlinear parameter estimation algorithm. This leads to a sparse and yet accurate representation of the pre-distorter, with the capability of tracking efficiently any rapidly time-varying behavior of the TWTA. Computer simulations results illustrate and validate the approach presented.
Keywords: Orthogonal Frequency Division Multiplexing, OFDM, Traveling Wave Tube Amplifier, TWTA.
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