A Doherty amplifier with maximally flat efficiency in the bandwidth

This contribution presents a creative circuit level solution to improve the efficiency versus frequency response of the Doherty amplifier. The proposed approach is compared with the conventional one and experimentally validated through a practical prototype realization based on GaN-HEMTs. Continuous wave measurements have shown a 65%-51% efficiency at about 42-36.5-dBm output power from 1.95-GHz to 2.25-GHz. When tested with a mobile WiMAX signal with 5MHz bandwidth and 9.3-dB Peak-to-Average Power Ratio (PAPR), the Doherty amplifier achieved an average efficiency around 50% with an Adjacent Channel Power Ratio (ACPR) lower than -38-dBc. Similar performances have been registered using a signal with 48-MHz bandwidth and 10.3-dB PAPR.