Implementation of a Two-Input Digitally Assisted Doherty Transmitter for Enhanced Performance

This work presents implementation of digitally assisted dual input Doherty power amplifier with enhanced performance in terms of power and efficiency. The efficiency enhancement is achieved by incorporating adaptive phase alignment mechanism. The alignment mechanism is implemented to characterize the imbalances between two inputs of Doherty power amplifier in terms of frequency dependent as well as power dependent phase. The proposed theory is validated with a 50 W Doherty power amplifier. The measured results show that the circuit gives upto 56% efficiency around 8-9 dB back-off, where, around 10% improvement is observed compared to its analog counterpart. The circuit also qualifies spectral mask when characterize with a single carrier 5 MHz modulated signal.