Characterization of the lossyness of matching networks for RF energy-harvesting rectennas

In general, a radio-frequency (RF) energy-harvesting rectenna uses the same structure as that for dedicated RF sources, although the level of input power is completely different. Few studies have investigated whether this situation needs a specific rectenna configuration, and the loss of rectenna elements for low-input-power scenarios has not yet been fully characterized. The purpose of this conference paper is to analyze the lossyness of impedance matching networks for RF energy-harvesting rectennas. The input power studied in this work ranges from -20 dBm to 0 dBm, and the rectenna is operated under such power levels at 900 MHz, 1.8 GHz, 2.4 GHz, and 5.8 GHz, respectively. We evaluate the additional loss of impedance matching networks comprising lumped capacitors, lumped inductors, or transmission lines in this situation, showing that the overall efficiency may decrease 95 percent in the worst case. Therefore, we suggest that the rectenna aiming at RF energy harvesting must remove the matching network, provided that the antenna impedance is directly conjugate matched to the input impedance of the rectifier.