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Implementation of dynamic bias and digital predistortion to enhance efficiency and linearity in a 100 W RF amplifier with OFDM signal

Published online by Cambridge University Press:  22 June 2009

Ludovic Bacque ,
Gregoire Nanfack-Nkondem ,
Philippe Bouysse ,
Guillaume Neveux ,
Jean Michel Nebus ,
William Rebernak ,
Luc Lapierre ,
Denis Barataud  and
Raymond Quéré
Ludovic Bacque
Affiliation:
XLIM – CNRS IUT GEII, 7 rue Jules Valles, 19100 Brive la Gaillarde, France.
Gregoire Nanfack-Nkondem
Affiliation:
XLIM – CNRS 123, Avenue Albert Thomas, 87060 Limoges Cedex, France.
Philippe Bouysse*
Affiliation:
XLIM – CNRS IUT GEII, 7 rue Jules Valles, 19100 Brive la Gaillarde, France.
Guillaume Neveux
Affiliation:
XLIM – CNRS 123, Avenue Albert Thomas, 87060 Limoges Cedex, France.
Jean Michel Nebus
Affiliation:
XLIM – CNRS 123, Avenue Albert Thomas, 87060 Limoges Cedex, France.
William Rebernak
Affiliation:
THALES Communications – 160 Boulevard de Valmy, 92704 Colombes, France.
Luc Lapierre
Affiliation:
CNES Toulouse – 18 Avenue Edouard Belin, 31055 Toulouse, France.
Denis Barataud
Affiliation:
XLIM – CNRS 123, Avenue Albert Thomas, 87060 Limoges Cedex, France.
Raymond Quéré
Affiliation:
XLIM – CNRS IUT GEII, 7 rue Jules Valles, 19100 Brive la Gaillarde, France.
*
Corresponding author: P. Bouysse Email: philippe.bouysse@xlim.fr
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Abstract

This paper presents a technique that enables both efficiency and linearity enhancements of power amplifiers (PA) used in communication systems. It consists in the implementation of a dynamic bias control combined with digital base-band predistortion. The aim of this paper is to describe a methodology and successive steps of the design procedure to reach optimum performances in terms of power added efficiency (PAE) and linearity. It is here applied to a 100 W wide-band lateral diffused metal oxide semiconductor (LDMOS) push–pull amplifier (50–500 MHz) driven by orthogonal frequency division multiplexing (OFDM) signals. When the amplifier is driven by a continuous wave (CW) signal and operates at a constant 28 V drain bias voltage, it exhibits 100 W output power and 60% PAE. When it is driven by an OFDM signal, a 10 dB output power back-off is necessary to have a −25 dBc adjacent channel power ratio (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 base-band digital predistortion provides additional linearity improvements at high PAE (for only one point PAE lost, a 5 dB improvement is obtained for ACPR).

Keywords

Smart power amplifierEnvelop trackingPower added efficiencyLinearityDigital predistortion
Type
Original Article
Information
International Journal of Microwave and Wireless Technologies , Volume 1 , Special Issue 4: European Microwave Week 2008 , August 2009 , pp. 261 - 268
Copyright
Copyright © Cambridge University Press and the European Microwave Association 2009

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References

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