A 135 GHz Direct-Digital 16-QAM Wireless and DWG Link

This chapter discusses the complete design of a 135 GHz direct-digital 16-QAM wireless and dielectric waveguide (DWG) link in 28 nm CMOS. The aim of this project was to develop a complete sub-THz link over a wireless and dielectric waveguide channel achieving very high data rates while trying to minimize the energy consumption of the system. First the challenges of conventional high-speed transceiver architectures are discussed, and the direct-digital system architecture is introduced. The complete 16-QAM system is described next and system-level specifications are determined. The circuit design of the transmitter and receiver is then elaborately discussed along with chip-level simulations. Design considerations of the high-frequency board are illustrated, including the on-board antenna and coupler. Finally, measurement results of the standalone chips and complete link are discussed, and the performance of the whole system is concluded.