## 4 Measurement Results  
A fabricated unit cell is shown in Figure 9 the actual unit cell is surrounded by square rings of 1 mm diameter metallic vias (10 \(\times\) 10 mm\({}^{2}\), 13 \(\times\) 13 mm\({}^{2}\)) to obtain electromagnetic connectivity between two WR62 waveguides through adopter conductors. The rectangular rings provide connectivity between the unit cell and the waveguide and help to avoid the different resonance modes of the substrate leaking out of the unit cell. There are two bias lines of width \(w_{b}=1\) mm that pass through the unit cell on both sides and end up with metallic pads to provide positive bias voltages to the PIN diodes. Two metallic lines with the same thickness are directly connected to the ground pass through the substrate, connected to the receiver structure, and end up on the ground pad at the top of the waveguide setup on the unit cell. The measured 3 dB transmission bandwidth (S\({}_{21}\)) lies between 14.12 and 18.02 GHz with a minimum insertion loss of 1.12 dB and 1.14 dB for state I (0\({}^{\circ}\)) and state II (180\({}^{\circ}\)) at 16 GHz. The reconciliation between the simulated and measured results is promising. The differences between the measured and simulated results are less than 3 dB throughout the desired band for both phase states. The measured results are similar for phase state I and state II as the consequence of the symmetric current reversal technique adopted in the proposed unit cell. There are fluctuations in the measured results because of the unstable behavior of the testing device and fabrication mismatch. The phase difference for both states are suitable for beam-scanning applications; the phase differences lie within 176-180 degrees. A complete comparison of the simulated and measured results is demonstrated below in Figure 10a. The measured phase shift results are illustrated in Figure 10b; the phase difference is stable with minor fluctuations and resonance on some points. The S\({}_{21}\) transmission phase difference observes that the minimum phase difference is not less than 176 degrees. Figure 9: Fabricated unit cell: (**a**) top view, (**b**) bottom view, (**c**) size reference unit cell. 5 Design and Optimization of 20 \(\times\) 20 Active Linearly Polarized Transmitarray for Ku Band  
In this section, we have characterized the feasibility of a wideband and low-profile structure design array using the proposed one-bit wideband meander-shaped hexagonal unit cell structure. The proposed 20 \(\times\) 20 transmitarray with a conventional method feed source is presented in Figure 8. Each side of the array is 160 mm (8.8 \(\times\)\(\lambda_{0}\)). The transmitarray has 400 PIN diodes to control the (0\({}^{\circ}\)/180\({}^{\circ}\)) phase distribution of the transmitted wave to achieve the desired radiation characteristics. The structure diagram of the horn feed is shown in Figure 11a and the size of the radiation port is 20 mm \(\times\) 20 mm. The radiation pattern of the horn feeds at 16.5 GHz was obtained by the simulation shown in Figure 11b. The half-power lobe widths corresponding to the two main planes are 69.96\({}^{\circ}\) and 66.2\({}^{\circ}\), respectively; the Q of the horn was obtained by fitting it with MATLAB. The value is 1.8, and the calculated optimum focal diameter ratio is 0.54. The performance of the TA was investigated on CST software for high-frequency simulation commercial tools. The array feed with a WR62 horn antenna with 10 dBi nominal gain located with focal distance, F = 112 mm (6.1\(\lambda_{0}\), F/D = 0.7), was used and is illustrated in Figure 12. The 20 \(\times\) 20 array max gain over frequency results are presented in Figure 13. The 3 dB gain bandwidth results are stable from 15.3 to conward through out graph. The DC bias network layout of a one-bit reconfigurable transmitarray has been considered  
Figure 11: Horn feed: (**a**) horn model (**b**) 17 GHz simulated radiation pattern.