Back-to-Back Microstrip Antenna Design for Broadband Wide-Angle RF Energy Harvesting and Dedicated Wireless Power Transfer

A novel back-to-back microstrip antenna is proposed to cover 2G/3G/4G/5G communication bands and ISM-2.4 GHz, ISM-5.8 GHz to simultaneously realize broadband wide-angle ambient wireless energy harvesting and dedicated wireless power transfer. The ground mode radiation is introduced by the limited-sized ground, with the loading of the patches and shorting vias, to form a broadband resonance from 2 GHz to 4 GHz. Furthermore, a resonance at ISM-5.8GHz is also excited with high-directivity. On the basis of ensuring miniaturization (e.g. $0.28\lambda _{0} \times 0.22\lambda _{0} \times 0.05\lambda _{0}$ for 2 GHz) and compactness, omnidirectional radiation in broadband resonance and bi-directional radiation at 5.8 GHz are realized by the `back-to-back' combination of two antenna elements. Measured results show that an over 67.2% impedance bandwidth (2.03 GHz~4.08 GHz) is obtained. Through the wireless power transmitting and receiving test, the angular stability of above ±60° for wireless energy harvesting is achieved at the mainstream operating frequencies. At ISM-2.4 GHz RF power of up to -8.5 dBm can be harvested at a distance of 0.5 m from the transmitter with the transmitting power of 12.5 dBm, while it is -8.9 dBm at ISM-5.8 GHz, which validates the effectiveness for WEH/WPT.