RF Energy Harvesting Using Complex-Conjugate Rectennas Along Single-Wire Transmission Lines

Goubau Single-Wire Transmission Lines (SWTL) enable low-loss long-distance links using surface waves confined to a single conductor. Here, the concept of harvesting RF energy in the near-field of a high-power SWTL is proposed, showing up to 25 mW and 30 V DC output from a wire excited with under 30 dBm of 902 MHz signals. The leakage from the SWTL is harvested using a flexible single-layer rectenna array based on six complex-conjugate electrically-small antennas with series power summation between the elements. 15 mW of DC power could be harvested at 4 m distance from the transmitter in proximity of an SWTL, compared to under
$150\ \mu\mathrm{W}$
in space. It is shown that SWTLs could enable long-range low-loss hybrid wireless power transmission (WPT).