A retrodirective beamforming system (BFS) based on a Rotman lens is proposed for far-field wireless power transfer at Ka-band. The true-time-delay property of the Rotman lens allows for a wideband operation covering 28–38 GHz. The designed BFS comprises a Rotman lens with nine beam ports connected to a nine-element linear Vivaldi array. The proposed BFS is implemented using PCB technology for ease of manufacturing and low-cost processing. The simulated and measured results demonstrate that the proposed BFS can generate nine discrete beams over a scan range of ±45° with a wide impedance bandwidth.
Rainbow-link: Beam-Alignment-Free and Grant-Free mmW Multiple Access using True-Time-Delay Array