Tutorial: Digital RF Transmitters

Direct digital-to-RF conversion at the antenna interface offers many exciting opportunities to push the performance envelope of RF transmitters in efficiency, area, signal bandwidth, and modulation quality. This tutorial will provide a complete overview of digital transmitter architectures, starting from digital bits at the symbol rate all the way to the antenna. We will start at the heart of this architecture, with a review of state-of-the-art, high-efficiency, digital PA topologies. Then we will discuss all auxiliary circuits and digital signal-processing tricks needed around the PA core to enable the transmitter to meet strict signal fidelity and spectrum cleanliness requirement while to simultaneously provide the PA core with the optimal environment for highest efficiency. Topics for discussion include: digital sample-rate conversion, 1-D and 2-D digital pre-distortion for wideband signals, and peculiarities of signal processing in the polar domain.