Linearization of Doherty Amplifier by Injection of Digitally Processed Baseband Signals at the Output of the Main and Auxiliary Cell

The linearization of a broadband two-way microstrip Doherty amplifier is performed by modified linearization approach that exploits the baseband nonlinear signals of the second-order. The required linearization signals adequately tuned in magnitude and phase in the digital domain modulate the second harmonics of fundamental carrier, which are then inserted at the outputs of the main and auxiliary amplifier transistors in the Doherty topology. The estimation of the proposed linearization method influence on a Doherty power amplifier is evaluated for two-tone baseband signal characterized by tone separation up to 30 MHz for several input signal power levels, and for OFDM digitally modulated signal.