Coupled Resonator-Based Metasurface Reflector with Enhanced Magnitude
and Phase Coverage
Abstract
A metasurface reflector unit cell is proposed for achieving
near-complete-range of complex reflectance (i.e., magnitude and phase)
for versatile beamforming capabilities. The unit cell is based on
coplanar coupled resonators: a split ring resonator (SRR) with a lumped
capacitor and a lumped resistor, and a dipole ring resonator (DRR) with
another lumped capacitor. The DRR inserted inside the SRR creates a
coupled resonance configuration which results in an enhanced complex
reflectance range at the desired frequency. To provide a physical
insight and explain the operation principle of the structure, the
response of the unit cell is modeled as a coupled Lorentz oscillator via
the effective surface susceptibilities, where a unique plasma, damping
constant, and resonant frequency can be attributed to each resonator.
The proposed unit cell is demonstrated in an array configuration for
linear-polarized beamforming, where full-wave simulations are used to
demonstrate beam-steering, gain control, side-lobe level control and
dual- and triple-beam generation, as illustrative examples. Finally
experimental demonstration is performed to validate the full-wave
results and obtain in-depth electrical characterization of the
reflectors.