A Unified Distortion Analysis of Nonlinear Power Amplifiers with Memory Effects for OFDM Signals

Yitao ZHANG  Kiyomichi ARAKI  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E93-C   No.4   pp.489-496
Publication Date: 2010/04/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E93.C.489
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Electromagnetic Theory
Keyword: 
nonlinear power amplifiers,  memory effects,  spectral regrowth,  adjacent channel power leakage power ratio (ACPR),  error vector magnitude (EVM),  orthogonal frequency-division multiplexing (OFDM),  complex Gaussian distribution,  

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Summary: 
Nonlinear distortions in power amplifiers (PAs) generate spectral regrowth at the output, which causes interference to adjacent channels and errors in digitally modulated signals. This paper presents a novel method to evaluate adjacent channel leakage power ratio (ACPR) and error vector magnitude (EVM) from the amplitude-to-amplitude (AM/AM) and amplitude-to-phase (AM/PM) characteristics. The transmitted signal is considered to be complex Gaussian distributed in orthogonal frequency-division multiplexing (OFDM) systems. We use the Mehler formula to derive closed-form expressions of the PAs output power spectral density (PSD), ACPR and EVM for memoryless PA and memory PA respectively. We inspect the derived relationships using an OFDM signal in the IEEE 802.11a WLAN standard. Simulation results show that the proposed method is appropriate to predict the ACPR and EVM values of the nonlinear PA output in OFDM systems, when the AM/AM and AM/PM characteristics are known.