Challenges in Adoption of RF to DC Converter for Micro-Scale RF Energy Harvesting Systems

This paper discusses and addresses the challenges encountered in designing an RF to DC converter (RDC) for RF energy harvesting applications. The challenges range from the choice of an appropriate topology to the low power conversion efficiency (PCE) exhibited by traditional RDCs at ultra-low power levels. It is shown that traditional RDC topologies demonstrates superior PCE at ultra-low power levels by replacing NMOS transistors with PMOS transistors. In addition to that, several circuit techniques adopted to further improve the PCE are discussed, and are classified into four different categories. Their performance is studied and compared for input power levels ranging from -30 dBm to 0 dBm, and the number of RDC stages. For a fair comparison, each topology has been realized using 0.18μm standard CMOS technology node and an operating frequency of 900 MHz. Based on the comparisons, recommendations on the choice of circuit techniques for different applications and operational scenarios are provided.