Fig. 1. (a) Schematic and (b) photograph of the symmetry-broken metasurface. The metallic pattern is copper with a conductivity of 5.8×107  S/m, and its depth is 0.035 mm. The 72.14  mm×34.04  mm×1.0  mm-substrate is Teflon with a relative permittivity of 2.65 and a loss tangent of 4×10−4. The geometric parameters of the metasurface are as follows: L1=32  mm, L2=26  mm, w=2  mm, g=1.3  mm, δ=3  mm, W=10  mm, and s=2  mm. A PIN diode is located at the center of the vertical wire. Two bias copper wires indicated by sky blue lines have a diameter of 0.1 mm.

Fig. 2. (a) Simulated transmission spectra of the vertical wire alone (green curve), horizontal wire alone (blue curve), and the symmetry-broken metasurface (red curve). (b) Schematic view of destructive interference between the bright and dark modes. (c) Simulated transmission phase (blue curve) and group delay (red curve) of the symmetry-broken metasurface. (d)–(f) Distribution of the electric field on the plane where the metallic pattern is located and the induced surface current indicated by arrows on the metallic pattern at 2.97 GHz. All these results are obtained when the resistance of the PIN diode is 2 Ω.

Fig. 3. (a) Transmission spectra of the symmetry-broken metasurface predicted by the TCMT (blue points) and simulated through FEM (red curve). (b) Magnitude of the electric dipole moment of vertical wire (pv, red curve) and horizontal wire (ph, blue curve) in the symmetry-broken metasurface. (c) Magnitude and (d) phase of p1 and p2. All these results are obtained when the resistance of the PIN diode is 2 Ω.

Fig. 4. (a) Simulated transmission spectra of the symmetry-broken metasurface and calculated magnitude spectra of p2, which represent the interaction between the vertical and horizontal wires for δ=0, 1.0, 2.0, and 3.0 mm. (b) Distribution of the electric field on the plane where the metallic pattern is located as δ varies from 0 to 3 mm at 2.97 GHz. All these results are obtained when the resistance of the PIN diode is 2 Ω.

Fig. 5. (a) Measured and (b) simulated transmission spectra of the vertical wire alone on substrate with the bias voltage ranging from 0 to 1.2 V, and accordingly the resistance of the PIN diode varying from 3000 Ω to 2 Ω.

Fig. 6. Transmission spectra of the symmetry-broken metasurface obtained through both (a) experiment and (b) simulation with the bias voltage ranging from 0 to 1.2 V, and accordingly the resistance of the PIN diode varying from 3000 Ω to 2 Ω.

Fig. 7. Measured transmittance of the symmetry-broken metasurface versus the bias voltage at 2.96 GHz (red curve), 3.11 GHz (green curve), and 3.76 GHz (blue curve).