## 3 Metasurface Simulation and Experimental Measurement Results
### Metasurface Experimental Measurement and Results  
The fabricated metasurface is fed by a broadband horn antenna that operates from 2 to 18 GHz and is measured by using the near-filed planar-scanning techniques in the anechoic chamber, as shown in Figure 7a. And the prototype of the fabricated reflective metasurface is shown in Figure 7b.  
Figure 5: (**a**) The compensation phase distribution of the designed metasurface; (**b**) the layout of the metasurface; (**c**) the normalized E-field amplitude distribution of the dual pseudo Bessel beams on the xoz-plane.  
Figure 6: Simulated normalized E-field amplitude distributions on the different observation planes at the distances of (**a**) 400 mm, (**b**) 600 mm, (**c**) 800 mm, (**d**) 1000 mm, and (**e**) 1200 mm away from the metasurface when the azimuth angle of the pseudo Bessel beam is 0\({}^{\circ}\). The simulated normalized E-field amplitude distributions on the different observation planes at the distances of (**f**) 400 mm, (**g**) 600 mm, (**h**) 800 mm, (**i**) 1000 mm, and (**j**) 1200 mm away from the metasurface when the azimuth angle of the pseudo Bessel beam is 180\({}^{\circ}\).  
A standard waveguide probe is used to detect the normalized E-field amplitude distributions corresponding to that shown in Figure 6. To detect the off-axis beams, the metasurface should have an inclined angle of \(\pm 30^{\circ}\) to the \(z\)-axis, and the scanning plane has a size of 0.3 m \(\times\) 0.3 m with a sampling grid of 5 mm. The normalized E-field amplitude distributions on the different observation planes are, respectively, perpendicular to the two propagation directions and have a distance from the metasurface of 400 mm, 600 mm, 800 mm, 1000 mm, and 1200 mm, measured as shown in Figure 8. The comparison between Figures 6 and 8 shows that the experimental measurement results of the dual pseudo Bessel beams are in good agreement with the simulated one.  
In order to show the phenomenon of dual pseudo Bessel beams, we observe the normalized E-field amplitude distributions of the dual-beams on a 1.2 m \(\times\) 0.6 m observation plane, which is perpendicular to the probe. The distance between the probe and the observation plane is 0.6 m, and the experimental measurement normalized E-field amplitude distribution on the observation plane is shown in Figure 9.  
Figure 8: Experimental measurement normalized E-field amplitude distributions on the different observation planes at a distance of (**a**) 400 mm, (**b**) 600 mm, (**c**) 800 mm, (**d**) 1000 mm, and (**e**) 1200 mm away from the metasurface when the azimuth angle of the pseudo Bessel beam is \(0^{\circ}\). The experimental measurement normalized E-field amplitude distributions on the different observation planes at a distance of (**f**) 400 mm, (**g**) 600 mm, (**h**) 800 mm, (**i**) 1000 mm, and (**j**) 1200 mm away from the metasurface when the azimuth angle of the pseudo Bessel beam is \(180^{\circ}\).  
Figure 7: (**a**) Experimental measurement scene of the dual pseudo Bessel beams in the anechoic chamber; (**b**) the prototype of the fabricated reflective metasurface.  
From the experimental measurement result shown in Figure 9, it is sure that the energy concentrates on the points where the pseudo Bessel beams pass through, and the amplitudes of the two beams are basically equivalent. So, we can draw the conclusion that the dual pseudo Bessel beams were generated by the metasurface, and almost all of the energy is propagating along the desired directions.