Novel design of a 10 dB back-off broadband sequential Doherty power amplifier for wireless applications

This paper presents the design and experimental results of a broadband sequential Doherty power amplifier (S-DPA). This new type of DPA allows large back-off (BO), highly efficient and broadband DPAs to be realised. A 10 W/10 dB BO S-DPA is designed to verify the design concept. Measurement results show obvious Doherty behaviour with 8 - 11 dB output power back-off over a 1.85 - 2.4 GHz frequency range. A drain efficiency of 65% over 300 MHz at BO and ≥ 58% over 500 MHz bandwidth at saturation is obtained. To show the state-of-the-art of the S-DPA, the drain efficiency at 2.0 GHz is selected with 74.5 % at saturation and 67.3% at 10 dB BO. Linearised measurement with a 10 MHz LTE signal having a crest factor of 7.5 dB at 2.1 GHz exhibits an average drain efficiency of 53% and an adjacent channel leakage ratio (ACLR) of -44.2/ - 48.7 dBc at an average output power of 32.7 dBm. To the best of the author's knowledge, this is the first wideband, 10 dB BO DPA with such high efficiency reported so far.