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Efficiency and Linearity of Digital "Class-C Like" Transmitters

: Mul, Dieuwert P.N.; Bootsman, Rob J.; Bruinsma, Quinten; Shen, Yiyu; Krause, Sebastian; Quay, Rüdiger; Pelk, Marco J.; Rijs, Fred van; Heeres, Rob M.; Pires, Sergio; Alavi, Morteza; Vreede, Leo C.N. de


Institute of Electrical and Electronics Engineers -IEEE-:
50th European Microwave Conference, EuMC 2021. Proceedings : 12-14 January 2021, Utrecht, The Netherlands
Piscataway, NJ: IEEE, 2021
ISBN: 978-1-7281-7039-8
ISBN: 978-2-87487-059-0
ISBN: 978-2-87487-058-3
4 S.
European Microwave Conference (EuMC) <50, 2021, Utrecht>
Fraunhofer IAF ()
Class-C; digital transmitter; efficiency; linearity; LDMOS; CMOS RFIC; polar transmitter; RFDAC; digital power amplifier

An energy-efficient, intrinsically linear, digital “class-C like” operation-mode is investigated for use in high-power digital transmitters (DTXs), which target next generation mMIMO base stations that offer lower costs, higher integration, and improved system efficiency. The proposed operation utilizes class-B/C output matching in combination with duty-cycle reduction and current-mode operation of a segmented output stage. Its performance in terms of efficiency, output power, and linearity is benchmarked with analog class-B/C operation. The proposed digital “class-C like” operation has been experimentally verified using a fully-digital, dual TX line-up with VT -shifted segmented LDMOS output stages. All output stage segments are individually controlled by high-speed digital drivers implemented in 40 nm CMOS technology. The realized prototype provides25.9 W (CW) output power with 75.7 % drain and 72.9 % system efficiencies, at 930 MHz and at 28 V drain supply.