High-Efficiency Envelope-Tracking W-CDMA Base-Station Amplifier Using GaN HFETs

Authors:
  • DKD.F. Kimball
    D.F. Kimball
  • JJJ. Jeong
    J. Jeong
  • CHC. Hsia
    C. Hsia
  • PDP. Draxler
    P. Draxler
  • SLS. Lanfranco
    S. Lanfranco
  • WNW. Nagy
    W. Nagy
  • KLK. Linthicum
    K. Linthicum
  • LLL.E. Larson
    L.E. Larson
  • PAP.M. Asbeck
    P.M. Asbeck
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Abstract
A high-efficiency wideband code-division multiple-access (W-CDMA) base-station amplifier is presented using high-performance GaN heterostructure field-effect transistors to achieve high gain and efficiency with good linearity. For high efficiency, class J/E operation was employed, which can attain up to 80% efficiency over a wide range of input powers and power supply voltages. For nonconstant envelope input, the average efficiency is further increased by employing the envelope-tracking architecture using a wide-bandwidth high-efficiency envelope amplifier. The linearity of overall system is enhanced by digital pre-distortion. The measured average power-added efficiency of the amplifier is as high as 50.7% for a W-CDMA modulated signal with peak-to-average power ratio of 7.67 dB at an average output power of 37.2 W and gain of 10.0 dB. We believe that this corresponds to the best efficiency performance among reported base-station power amplifiers for W-CDMA. The measured error vector magnitude is as low as 1.74% with adjacent channel leakage ratio of -51.0 dBc at an offset frequency of 5 MHz

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