ZTE

ZTE Communications ›› 2011, Vol. 9 ›› Issue (3): 22-27.

• Special Topic • Previous Articles     Next Articles

FPGA Implementation of a Power Amplifier Linearizer for an ETSI-SDR OFDM Transmitter

Suranjana Julius and Anh Dinh   

  1. Department of Electrical and Computer Engineering, University of Saskatchewan, Saskatoon, S7N 5A2, Canada
  • Online:2011-09-25 Published:2011-09-25
  • About author:Suranjana Julius (suj967@mail.usask.ca) received her BSc degree in electronics and communication engineering from Bangalore University in 2002. Between 2002 and 2007, she worked in India and South Africa in various R&D positions and also worked as an applications engineer. Suranjana received her M.Sc. degree from the University of Saskatchewan, Canada, in 2010. Her research interests include digital signal processing, software defined radio, and digital logic design for FPGAs.

    Anh Dinh (anh.dinh@usask.ca) received his B.Sc. degree in electrical and computer engineering from Lakehead University, Canada, in 1992. He received his M.Sc. and Ph.D. degrees from the University of Regina, Canada, in 1997 and 2000. He currently works at the Department of Electrical and Computer Engineering at the University of Saskatchewan. His research interests include biosensors and very large scale integration (VLSI) for wireless communications.

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Abstract: Most satellite digital radio (SDR) systems use orthogonal frequency-division multiplexing (OFDM) transmission, which means that variable envelope signals are distorted by the RF power amplifier (PA). It is customary to back off the input power to the PA to avoid the PA nonlinear region of operation. In this way, linearity can be achieved at the cost of power efficiency. Another attractive option is to use a linearizer, which compensates for the nonlinear effects of the PA. In this paper, an OFDM transmitter conforming to European Telecommunications Standard Institute SDR Technical Specifications 2007-2008 was designed and implemented on a low-cost field-programmable gate array (FPGA) platform. A weakly nonlinear PA, operating in the L-band SDR frequency, was used for signal transmission. An adaptive linearizer was designed and implemented on the same FPGA device using digital predistortion to correct the undesired effects of the PA on the transmitted signal. Test results show that spectral distortion can be suppressed between 6-9 dB using the designed linearizer when the PA is driven close to its saturation region.

Key words: power amplifier linearization, digital predistortion, ETSI-SDR, OFDM, FPGA