High efficiency CDMA RF power amplifier using dynamic envelope tracking technique

Abstract

This work describes a 2-W peak-envelope linear power amplifier based upon the envelope tracking (ET) technique with application to CDMA cellular radio handsets. Both drain voltages of a two stage monolithic GaAs IC are varied with respect to the long term rms value of the modulated signal using a high efficiency Class-S modulator. The modulator is implemented as a single chip silicon IC to supply currents in excess of 1 A. The RF amplifier IC utilizes two AlGaAs/InGaAs heterostructure insulated-gate FET structures which allows single voltage supply operation with state-of-the-art linearity and efficiency performance. When driven by a CDMA O-QPSK signal, the ET amplifier exhibits desired spectral linearity while achieving a remarkable 5/spl times/ improvement in overall efficiency, compared to fixed supply bias, when measured in a reverse link urban based mobile transmitter power profile.