Fig. 1. Geometry of the proposed 2-bit element: (a) 3D view, (b) top view, and (c) bottom view. (h₁ = 0.508 mm, h₂ = 0.1 mm, h₃ = 0.203 mm, d = 5.60 mm, l₁ = 1.82 mm, l₂ = 0.63 mm, l₃ = 0.41 mm, w₁ = 0.60 mm, w₂ = 0.59 mm, l₄ = 1.60 mm, l₅ = 1.00 mm, l₆ = 0.90 mm, w₃ = 0.43 mm, w₄ = 0.50 mm, w₅ = 0.38 mm, w₆ = 0.43 mm, and w₇ = 0.35 mm)

Fig. 2. Equivalent circuit of p-i-n diode.

Fig. 3. When the antenna unit operates in different mode states, the surface current distributions of the top radiation patch and the bottom phase shifter: (a) state 1, (b) state 2, (c) state 3, and (d) state 4.

Fig. 4. Simulated results under different antenna modes: (a) reflection coefficients and ARs, (b) far-field phases, (c) gain pattern at 27 GHz, φ = 0° plane, and (d) gain pattern at 27 GHz, φ = 90° plane, where CS stands for complete structure, WBPS represents without bottom phase shifter, and WBPSTP represents without bottom phase shifter & top p-i-n diodes.

Fig. 5. 1×8 array exploded view.

Fig. 6. Fabricated array sample: (a) top view, (b) bottom view, and (c) experimental configuration in the anechoic chamber.

Fig. 7. Measured results of the broadside beams at φ = 90° plane: (a) |S₁₁ | and (b) gain and directivity at 0°.

Fig. 8. Measured gain patterns of scanning beams at 27 GHz, φ = 90° plane.

Table 1. Comparison between other relevant researches.

Table 2. Antenna status defined by different codes of p-i-n diodes.

Table 3. Performance indexes of measured beams.