High Efficiency and Linear Power Amplification for OFDM Signal by Combining Dynamic Bias and Digital Baseband Predistortion

Ludovic Bacqué (1) , Grégoire Nanfack Nkondem (1) , Philippe Bouysse (1) , Guillaume Neveux (1) , W. Rebernak , C. Poumier , L. Lapierre , Denis Barataud (1) , Raymond Quéré (1)

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This paper presents a technique that enables both efficiency and linearity enhancements for power amplifiers (PA) used in communication systems. It is here applied to a 100 W wide-band LDMOS push-pull amplifier (50-500 MHz) driven by OFDM signals. When the amplifier is driven by a CW signal and operates at a constant 28 V drain bias voltage, it exhibits 100 W output power with 60% Power Added Efficiency (PAE). When it is driven by an OFDM signal, a 10 dB output power back-off is necessary to have a -25 dBc ACPR and PAE decreases down to 10%. By properly implementing an envelope tracking bias system 40 W output power along with 38% PAE and -27 dBc ACPR have been reached. Applying baseband digital predistorsion provides additive improvements at high PAE (for only 1 point PAE lost the ACPR increases of 5 dB).

Ludovic Bacqué, Grégoire Nanfack Nkondem, Philippe Bouysse, Guillaume Neveux, W. Rebernak, et al.. High Efficiency and Linear Power Amplification for OFDM Signal by Combining Dynamic Bias and Digital Baseband Predistortion. European Microwave Week, Oct 2008, Amsterdam, Netherlands. pp. 1687 - 1690, ⟨10.1109/EUMC.2008.4751799⟩. ⟨hal-00660741⟩