A 26–40GHz 4-Way Hybrid Parallel-Series Role-Exchange Doherty PA with Broadband Deep Power Back-Off Efficiency Enhancement

This paper presents a hybrid parallel-series Doherty power amplifier (PA) architecture that supports broadband operation and deep power back-off (PBO) efficiency enhancement to support next-generation wireless communication. The architecture builds on hybrid use of broadband parallel- and series-type coupled-line Doherty power combiners with four PA paths. The wide carrier bandwidth is achieved by exploiting different frequency dependent active load-modulations of the parallel/series Doherty combiners and PA path biasing reconfigurations, while the deep PBO is realized by the optimum turn-on sequences of the four PA paths. As a proof-of-concept design, a 26–40 GHz PA is implemented in GlobalFoundries 45nm CMOS SOI process. The PA measures 22.5–23.9 dBm OP1dB, 26.2–38.2% PAEOP1dB, 18.1–34.5% PAE6dB PBO, and 10.7–22.1% PAE12dB PBO. Note the PBO levels are referenced from OP1dB. Compared to a normalized ideal class B PA, this design achieves 1.3–1.8× PAE boost at 6dB PBO, and 1.6–2.3× boost at 12dB PBO. With a 250MSym/s 64-QAM signal, this PA achieves 16.1 dBm Pave and PAEave of 30.7% at an EVMrms of -25.3 dB. With a 100Msym/s 256-QAM signal, this PA achieves Pave of 13.5 dBm and PAEave of 26.2% at an EVMrms of -31.3 dB.