An Orthogonally-Polarized Multi-Beam Rectenna System to Imitate Isotropic DC Pattern for Orientation-Insensitive Microwave Power Delivery

The Wireless Power Transfer (WPT) rectenna systems suffer from low power conversion efficiency (PCE) due to lower receiver (Rx) gain, polarization mismatch, and angular misalignment that can occur between the transmitter (Tx) and receiver (Rx). This impedes the realization of self-sustaining freely-rotating IoT sensor nodes. To address this issue, an orthogonally-polarized, multi-beam, orientation-insensitive WPT system is proposed to achieve a nearly isotropic DC pattern. The system employs orthogonally-polarized end-fire rectennas (Rect-I & Rect-II) in each sector and a centrally placed cross-polarized patch rectenna (Rect-III) to attain 3D DC coverage. Further, the antenna and rectifier circuit are conjugately matched to achieve miniaturization. A fully integrated hybrid DC combining topology and a smart bypassing network is employed to minimize combining losses. The three rectenna elements offer a PCE of 51 %, 44.9 %, and 58.9 %, with an open-circuit harvested DC voltage of 1600 mV. Thus, orthogonally-polarized, nearly isotropic DC pattern and polarization insensitivity of the proposed multi-beam rectenna system (MBRS) makes it suitable for powering small battery-less IoT sensor nodes.