Triple-Band RF Energy Harvesting System Using TDM Combiner Drawing 1.5 μW in 22nm FDSOI Technology

This work presents an RF energy harvesting system capable of combining power from three distinct frequencies: 900 MHz, 1.8 GHz, and 2.4 GHz. A Time Division Multiplexing (TDM) based combiner efficiently integrates the outputs of individual frequency-specific harvesters. The combiner uses voltage level detection to dynamically determine sufficient power delivery from each harvester. This enables the system to operate under various input scenarios, including all three frequencies available, two frequencies available, or a single frequency available. Importantly, the combiner adds currents at the output, maximizing power delivery to the load. The system achieves a total combining efficiency of $74.84 \%$ when all three inputs are present. For two-frequency operation, efficiencies range from $\mathbf{7 6 . 7 8 \%}$ to $\mathbf{8 7 . 4 3 \%}$ the combining efficiencies are $\mathbf{8 5 . 5 2 \%}$ for $\mathbf{9 0 0}$ MHz and $\mathbf{1 . 8} \mathrm{GHz}$ only, $87.43 \%$ for 900 MHz and 2.4 GHz only and $\mathbf{7 6 . 7 8 \%}$ for $\mathbf{1 . 8 ~ G H z}$ and 2.4 GHz only. For single-frequency operation, the efficiencies are $\mathbf{9 0 . 9 5 \%}$ ($\mathbf{9 0 0} \mathbf{M H z}$), $\mathbf{9 4 . 7 6 \%}$ ($\mathbf{1 . 8}$ $\mathbf{G H z}$), and $\mathbf{9 2 . 1 5 \%}$ ($\mathbf{2 . 4} \mathbf{G H z}$). The combiner maintains low power consumption, drawing only $1.5 \mu \mathrm{~W}$ at a 0.8 V supply.