Low-Directivity High-Gain Rectenna Array for Improving Power-Harvesting Efficiency on 5.8GHz Batteryless Transponder

Dedicated Short Range Communication battery-less transponders require capability of harvest RF energy without the necessity of standing perfectly in front of the radio transmitter. Harvesting efficiency is improved increasing the receiving antenna gain, but this reduces the field-of-view for energy transfer. This work introduces an architecture based on an array of rectennas, each one implementing a patch antenna, connected to a single commercial DC/DC step-up converter. Without combining the patches in a phased array the low directivity of each patch keeps wide the energy harvesting field-of-view, while harvesting efficiency is preserved by gathering together the DC currents provided by each rectenna. In measurements involving a 5.8GHz continuous-wave excitation, the array of rectennas produced a current of 730 µA with signal on boresight direction and of 560 µA at 30 degrees of tilting, compared to 680 µA and 192 µA as expected for a phased array with a comparable patches displacement.