*4.2. Experimental Results*

To demonstrate the capability of the proposed coding metasurface, after fabricating, several tests were done with the prototype.

## 4.2.1. Beam Steering with Beam Synthesis Scheme

In the first test, we applied ON/OFF coding patterns, which were calculated using the beam synthesis scheme, to verify the beam steering capability of the metasurface. The metasurface is attached to a holder which is perpendicular to the horizontal plane as shown in Figure 7b. A horn antenna working as an EM source is placed at (10 mm, −5.7 mm, 0 mm) with respect to the metasurface to avoid blocking the reflected signal. The measured results are presented in Figure 12.

**Figure 12.** The measured normalized radiation pattern.

We can observe that the coding metasurface can perform beam focusing and steering to a specific direction with the elevation angle (*θ*) range of 0◦ to 60◦. As a matter of fact, the steerable elevation angle can range from −60◦ to 60◦ and the azimuth angle, which the main beam can be focused on, is (0◦, 360◦) by properly assembling the feed horn. However, in the limitation of this paper, we would not demonstrate these results. Further, there are constant errors of about 2◦ occurred in every cases that may be caused by the imperfection of the experimental setup. Moreover, similar to the theory, the grating lobe appears in the case of steering the beam to 50◦ and 60◦. It is the limitation of the planar metasurface. In addition, the half-power beamwidth (HPBW) ranging from 13◦ to 27◦ is likely large

due to the small size of the coding metasurface. A much sharper beamwidth can be attained with a larger coding metasurface.
