Power Efficiency of OFDM Signal Amplification with Doherty and Extended Doherty Transmitters

Konferenz: European Wireless 2008 - 14th European Wireless Conference
22.06.2008 - 25.06.2008 in Prague, Czech Republic

Tagungsband: European Wireless 2008

Seiten: 5Sprache: EnglischTyp: PDF

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Yamao, Yasushi; Toyama, Yoshikazu; Umali, Edwin M. (Advanced Wireless Communication Research Center, the University of Electro-Communications, 1-5-1 Chofugaoka, Chofu-shi, Tokyo, 182-8585, Japan)

OFDM (Orthogonal Frequency Division Multiplex) achieves high spectral efficiency in broadband wireless communications but has poor amplification efficiency due to its large peak-to-average power ratio. This paper presents achievable average power efficiency for the OFDM signal when the Doherty and extended Doherty transmitters are employed. By modelling the envelope of OFDM signal as a Rayleigh-distributed signal, average power efficiency for the OFDM signal is calculated as a function of clipping provability. Numerical calculation results assuming an ideal class-B amplifier and predistortion linearizer show that average drain efficiency of the two amplifiers for a clipping probability of 0.1% are 50.5 and 55.6 %, respectively. It is concluded that the extended Doherty amplifier can improve power efficiency by several percents by optimizing the main amplifier contribution ratio α.