Bits-In RF-Out Transmitters

To address ever-increasing demand in the 5G cellular network, radio-frequency (RF) transmitters (TX) are currently reinvented and directed towards more digital intensive configuration. These advanced architectures, which convert the input digital baseband data directly into RF signal, i.e., “bits-in RF-out,” must be wideband and energy-efficient. Moreover, to support multiband/multi-mode operation and to meet the stringent spectral purity requirements of communication standards, they should be frequency-agile and highly linear. In this workshop, we describe the strengths, possibilities, and challenges of the bits-in RF-out TXs. We categorize TX into two prominent configurations, polar and Cartesian (I/Q). Next, the concept of mixing (RF)-DAC-based TX, their advantages and limitations are studied. Finally, to address their challenges, such as an efficient operation at 6–10 dB power back-off as well as a reasonable spectral purity while managing an aggregated bandwidth of 100MHz, we review some of our recent bits-in RF-out CMOS TX prototypes.