Fig. 1. Schematic of the proposed antenna and the basic performance parameters, （a） Top view, （b） Side view, （c） Reflection coefficient S11, and （d） Simulated radiation patterns in E-plane for the two working states of the antenna （states 1 and 2 for the cases of unbiased and biased）

Fig. 2. （a） Schematic of the antenna with two groups of directors, （b）Reflection coefficient S₁₁, （c） E-plane radiation pattern and （d） θ=60° plane radiation pattern of the proposed antenna operating at different states.

Fig. 3. （a） Structure of the antenna with three groups of directors, （b） Reflection coefficient S₁₁ of the proposed antenna operating at different states, （c） E-plane radiation pattern, and （d） Radiation pattern in θ=60° plane

Fig. 4. （a-1）~（a-4） and （b-1）~（b-4）, 3D radiation patterns in different planes.（c-1）~（c-4） Surface current （J_s） distributions for the proposed antenna in different working states. （a-1）, （b-1）, and （c-1） for state 1; （a-2）, （b-2）, and （c-2） for state 2; （a-3）, （b-3）, and （c-3） for state 3; （a-4）, （b-4）, and （c-4） for state 6.

Fig. 5. （a） and （b） Radiation patterns of antenna proposed in Section 2.2, （a） With different electron relaxation times in graphene, （b） With and without p-doped silicon strips,（c） and （d） Radiation patterns of antenna proposed in section 2.1, （c） With different bias voltages applied to the graphene-patch directors, and （d） With graphene-patch directors with µ_c=0 eV and without graphene-patch directors.

Table 1. Antenna parameters （units: µm）

Table 2. Antenna performance