A load-modulated low-power amplifier with average power tracking

A supply- and load-modulated RF power amplifier is proposed for applications in which output power control is required. The drain supply is scaled in harmony with the required average output power using a switch-mode power supply (SMPS), while the load is modulated in harmony with the signal´s instantaneous envelope, to enhance average efficiency at each output power level. The concept is demonstrated with a 100mW GaAs amplifier operating at 2.35GHz, designed using discrete components. The amplifier is tested using WCDMA and LTE signals. The proposed architecture sustains high efficiency and good linearity over a large dynamic range, while it requires only a single set of control functions.