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.