Coupled Resonator Configuration for Enhanced Reflectarray Magnitude and Phase Control

A reflectarray metasurface unit cell consisting of two coupled resonators and three variable controls is proposed. The configuration consists of an outer split-ring resonator (SRR) responsible for resonance at the desired frequency and includes two variable elements; one capacitive and one resistive. A dipole-ring resonator (DRR) is inserted inside the SRR with a capacitive element, creating a resonance at a higher frequency than the SRR. Variation of the DRR resonance affects both the magnitude and the phase of the lower resonance of the SRR. For any given constraint on the available capacitive or resistive values, the coupled resonator configuration provides a significantly enhanced reflection magnitude and phase variations compared to a single isolated resonator. Control over magnitude and phase is used to demonstrate four cases of beamforming in the X-band at 9 GHz: side-lobe level (SLL) reduction, beam-steering, beam-steering with SLL reduction, and dual-beam generation.