This paper presents the first Arbitrary Waveform Generator (AWG) based on Walsh’s theory for wideband radio frequency (RF) conversion. The architecture is dedicated to 5G-FR1 applications (sub-6GHz) to perform a direct and large bandwidth conversion while achieving the highest energy efficiency. The circuit generates Walsh sequences weighted by Walsh coefficients thanks to dedicated Digital-to-Analog Converters (DACs). It embeds an internal memory to feed the data to be converted for measurement purposes. The sum of the weighted Walsh sequences carries out RF signals made of intrinsically synchronous aggregated channels over a frequency range between 600 MHz and 4 GHz. A high-level simulation study is performed as well as transistor-level simulation including post-layout and Monte-Carlo analysis. The circuit is designed in 28nm FD-SOI CMOS technology from STMicroelectronics. The power consumption is 44 mW depicting an energy per bit of 0.34 pJ/bit, the lowest of the state of the art to the authors’ knowledge.