An 18.5 W Fully-Digital Transmitter with 60.4 % Peak System Efficiency
A high-power digital transmitter (DTX) concept, targeting future mMIMO base stations, is presented. The proposed approach bridges the “historical” gap between low-voltage high-speed digital and high-voltage high-power RF devices. This combination allows for a complete replacement of the traditional TX line-up, which includes signal-generation, up-conversion, and analog pre-drivers and PA, as such facilitating energy savings. The DTX principles are demonstrated by a dual TX line-up implemented in a dedicated LDMOS technology. Each DTX line-up features 15-thermometer and 7 binary-weighted LDMOS output-stage segments, which are individually controlled by digital logic and high-speed drivers implemented in 40nm CMOS technology. The realized DTX exploits a 2.1GHz class-BE output matching network and provides 18.5W output power with 66.7% drain and 60.4% system efficiencies. The suitability of the concept to handle modulated signals is demonstrated for a two-tone signal, yielding an IM3<-51.4dBc and a 10MHz 256-QAM signal, achieving an ACLR of -46.1dBc and 1.2% EVM.