A high efficiency WCDMA power amplifier with pulsed load modulation (PLM)

  • Authors:

  • Shuhsien Liao;Yuanxun Ethan Wang

  • Affiliations:

  • Department of Electrical Engineering, University of California Los Angeles, Los Angeles, CA;Department of Electrical Engineering, University of California Los Angeles, Los Angeles, CA

  • Venue:
  • RWS'10 Proceedings of the 2010 IEEE conference on Radio and wireless symposium
  • Year:
  • 2010

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Abstract

A GaAs pHEMT power amplifier module designed for Pulsed Load Modulation (PLM) technique on Envelope Delta Sigma Modulation (EDSM) transmitter architecture is developed in this work. The dynamic impedance behavior origin from PLM technique provides efficiency enhancement and linear power modulation simultaneously. Comparing with conventional Class B mode power amplification, efficiency profile versus power back-off level is significantly improved. The system linearity for complex modulation signals is obtained through pulse based coding schemes and filtering in EDSM architecture. In this paper, a 1.87GHz PLM power amplifier module is fabricated and tested. The testing results show a maximum of 59.5% drain efficiency and maximum 29dBm output power including 0.8dB output filter loss for constant envelope signal. Comparing to conventional Class-B mode operation, the PLM technique offered improved power efficiency by 57.4% at 6dB power back-off and 76.9% at 10dB power back-off. The PLM amplifier module has been tested by WCDMA signal with 10.8dB peak to average power Ratio (PAR). At the output power of 26.3dBm, the amplifier has achieved 43% power added efficiency (PAE) and 39dBc ACLR at 5MHz offset without using any additional linearization techniques. If the filter loss is removed from the efficiency calculation, the actual achieved PAE by the PA is above 50%.