High efficiency feedforward power amplifier using a nonlinear error amplifier and offset alignment control

Abstract

A high efficiency feedforward power amplifier (FFPA) is proposed that uses the Doherty configuration for the both the main amplifier (MA) and error amplifier (EA). Using a nonlinear EA is a deviation from the traditional FFPA. A loop control algorithm is proposed that offsets the alignment setting from the standard value to best utilize the power handling capability and linearity of the MA and EA. A system efficiency of 25% is achieved for a rated output power of 52.7 dBm, while exceeding the WCDMA specifications. Reducing the peak-to-average power ratio (PAPR) of the input signal to 8 dB and using offset control improves the ACLR performance to -62 dBc.