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Power amplifier optimization using base band and multiharmonic source/load-pull characterization with digital predistortion

Published online by Cambridge University Press:  19 June 2009

Ghalid Idir Abib
Affiliation:
UPMC – L2E – Site Raphael – 3, rue Galilée – 94200 Ivry-Sur-Seine, France.
Eric Bergeault*
Affiliation:
Telecom ParisTech, Laboratoire Radiofréquences et Micro-ondes, Département COMELEC, 46, rue Barrault, 75634 Paris Cedex 13, France. Phone: 00-33-1-45-81-77-01; Fax: 00-33-1-45-80-40-36.
Souheil Bensmida
Affiliation:
Centre for Communications Research, University of Bristol, Merchant Venturers Building, Woodland Road, Bristol BS8 1U, UK.
Reda Mohellebi
Affiliation:
Telecom ParisTech, Laboratoire Radiofréquences et Micro-ondes, Département COMELEC, 46, rue Barrault, 75634 Paris Cedex 13, France. Phone: 00-33-1-45-81-77-01; Fax: 00-33-1-45-80-40-36.
*
Corresponding author: E. Bergeault E-mail: [email protected]

Abstract

In this paper, different techniques are combined in a unique characterization system dedicated to power transistor linearity improvement. Successive optimizations are performed using source-pull/load-pull techniques at fundamental, harmonic, and base-band frequencies associated with an instantaneous memoryless base-band predistortion procedure. Measurement results performed at 1.575 GHz on a metal semiconductor field effect transistor (MESFET) power device biased in class-AB under a quadrature phase shift keying (QPSK)-modulated signal excitation show that fundamental frequency load-pull increases the output power and power-added efficiency (PAE) by 2 dB and 16 percentage points, respectively. The fundamental frequency source-pull measurements lead to an adjacent channel power ratio (ACPR) variation equal to 3 dB. For harmonic load-pull (at 2f0), it has been found that some impedances greatly improve linearity but output power and PAE decrease. Source-pull characterization at the second harmonic frequency allows one to find a trade-off between output power, efficiency, and linearity. Moreover, the influence of base-band impedance on ACPR and error vector magnitude (EVM) is found to be 15 dB and 5.5 percentage points, respectively. Finally, instantaneous memoryless base-band predistortion improves ACPR and EVM values by 5 dB and 1 point, respectively.

Type
Original Article
Copyright
Copyright © Cambridge University Press and the European Microwave Association 2009

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References

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