Simplified Two-Dimensional Optical Beamforming Network Based on Cascade Microring Resonators in All-Pass Filter Configuration

We propose a two-dimensional (2-D) optical beamforming network (OBFN) using cascade microring resonators (MRRs) in all-pass filter configuration. The cascade MRRs can obtain a maximum time delay of greater than 100ps within a radio frequency (RF) range of more than 1.0GHz in
$28\text{GHz}$
band. For
$4\times 4$
2-D antenna array, the OBFN architecture utilizes only 8 cascade MRRs, and can scan the beam with wide coverage of -60° to 60° in the transverse and longitudinal directions simultaneously. This simplified OBFN architecture is promising to be applied in millimeter-wave communications.