Fully-digital transmitter architectures and circuits for the next generation of wireless communications

The rapidly evolving trend for increased data rates in today’s and future cellular communication systems poses extreme difficulties for developers of cellular transceivers. A multitude of standards ranging from legacy 2G to the upcoming, yet to be defined, 5G needs to be supported across a broad but fragmented frequency spectrum. Higher data throughput necessitates higher bandwidths, increased number of aggregated carriers, and more complex of modulation schemes. Capable transmitters must exhibit highest in-band performance, e.g. linearity and error vector magnitude. Simultaneously, out-of-band performance, like noise and spurious emissions, is crucial to co-exist with other wireless channels, such as the transceiver’s receivers and other participants. While a “more of everything” is expected, competitive solutions for the wireless market require a constant decrease in silicon area, bill of materials, and especially power consumption. This paper presents the evolution of integrated transmitter architectures facing the above challenges: From conventional analog direct conversion transmitters to fully-digital direct modulation RF transmitters, challenges and benefits are highlighted, presenting modern architectures that benefit from the most advanced technology nodes while supporting upcoming 5G cellular wireless communications.