RF Power Amplifier Efficiency Enhancement by Envelope Injection and Termination for Mobile Terminal Applications

An improved technique to enhance the efficiency of the linear RF power amplifiers (PAs) used in mobile terminal applications is proposed. The baseband load impedance is optimized, and the input envelope, along with the RF signal, is fed to the PA input. The resulting baseband modulation of the drain increases the saturated RF output power for a given dc power consumption. Digital predistortion is implemented to compensate for the linearity degradation. A 1.95-GHz heterojunction GaAs field-effect transistor PA, which in typical bias condition draws 100 mA from an 8.0-V supply and provides maximum power of 28 dBm for a continuous-wave input at 1.95 GHz, exhibits a significant improvement in peak power-added efficiency from 40% to 56% for a two-tone input, from 33% to 42% for an uplink WCDMA with one dedicated physical data channel (DPDCH), and from 27% to 32% for an uplink WCDMA with six DPDCHs.