Design of a broadband three-way sequential Doherty power amplifier for modern wireless communications

This paper presents the design and implementation of a broadband 3-way sequential-based Doherty power amplifier (DPA). This design approach can also be extended for a broadband N-way DPA architecture. A 12 - 23.5 W 3-way DPA has been designed, implemented and characterised to verify the proposed technique. The measured drain efficiency of 55 - 69 % over 500 MHz at 12 - 14 dB output power backoff (OBO) and 60 - 75 % over 600 MHz at saturation is achieved. Single-tone measurement at 2.1 GHz exhibits a drain efficiency of 63 %, 62.5 % and 75 % at 13.6 dB, 6 dB and 0 dB OBO, respectively. Also at this frequency, linearised measurement with a 10 MHz-LTE signal having a crest factor of 8.2 dB shows an average drain efficiency of 59 % and adjacent channel leakage ratio (ACLR) better than -45.5/ - 45.7 dBc at an average output power of 34.5 dBm. To the best knowledge of the authors, this is the first broadband 3-way sequential Doherty power amplifier with such high performance reported so far.