A Large Planar Holographic Reflectarray for Fresnel-Zone Microwave Wireless Power Transfer at 5.8GHz
We present a 5.8 GHz Fresnel-zone microwave wireless power transfer experiment leveraging a large planar holographic metasurface reflectarray to form a focused spot at a distance of 6.5 m. The 1.5 m² holographic metasurface is fabricated from 15 panels having total dimensions of 122×127 cm, and is comprised of over 4,000 reflective patch resonators on the top surface of a 3.0 mm thick FR-4 substrate. A constrained hologram approach is used to discretize the desired hologram and approximate the desired focal spot given the Lorentzian coupled amplitude-phase response of the patch resonators. When the metasurface is illuminated by a 20 dB standard-gain horn 1.8 m away, it produces a spot with a 3 dB beam waist (FWHM) of approximately 50 cm. The experimentally measured beam profile matches the simulated beam profile to ±1 dB within the beam, and we estimate almost 40% of the transmitted power was incident onto the receiver at the focus point.