# A Low-Profile Dual-Polarized Transmitarray with Enhanced Gain and Beam Steering at Ku Band
## 5 Simulation and Experimental Results of the TA Antenna  
The TA design outlined above does not take in account the feed's primary pattern, the phase discretization, transmission losses, or mutual coupling of the UC. To accurately assess these effects, full wave simulations with CST have been carried out. We fabricated and characterized the TA. Figure 10 presents the fabricated prototype and anechoic chamber measurement, with results compared to simulations. Figure 11 shows the simulated and measured peak gain of the feed antenna without TA and with TA conditions along with the measured aperture efficiency. It is observed from Figure 11 that the simulated realized peak gain is G\({}_{\text{s0}}\) = 23.35 dB, whereas measured peak gain is G\({}_{\text{m0}}\) = 21 dB at f\({}_{\text{0}}\) = 12 GHz. At f\({}_{\text{1}}\) = 12.4 GHz, the peak gain of this TA for simulation and measurement are G\({}_{\text{s1}}\) = 22.46 dB and G\({}_{\text{m1}}\) = 19.97 dB, respectively. The highest aperture efficiency is \(\text{t}_{\text{mxx}}=19\%\) at f\({}_{\text{2}}\) = 11.2 GHz, whereas it is \(\text{t}_{\text{0}}\) = 17% and \(\text{t}_{\text{1}}\) = 13% for f\({}_{\text{0}}\) = 12 GHz and f\({}_{\text{1}}\) = 12.4 GHz, respectively. It is observed that the 1 dB gain bandwidth is BW\({}_{\text{g}}\) = 10.8% (11.1-12.4 GHz). Figures 12 and 13 show the radiation pattern at f\({}_{\text{0}}\) = 12 GHz and f\({}_{\text{1}}\) = 12.4 GHz, respectively for E and H plane. The measured peak gains at f\({}_{\text{0}}\) = 12 GHz and f\({}_{\text{1}}\) = 12.4 GHz are \(\triangle\)G\({}_{\text{0}}\) = 2.35 dB and \(\triangle\)G\({}_{\text{1}}\) = 2.03 dB, less than the simulated gain for both E and H plane, respectively. This difference can be ascribed to larger insertion loss, due  
Figure 9: (**a**) Ray transmission through TA; (**b**) phase compensation obtained at f\({}_{\text{0}}\) = 12 GHz for focal distance F to diameter D ratio of 0.6.  
to thin air layer in between the substrates that have not been bonded together with prepreg, and other fabrication tolerances. The measured peak side lobe levels are \(\mathrm{SLL}_{0}=-20.8\) dB and \(\mathrm{SLL}_{1}=-18.5\) dB for \(\mathrm{f}_{0}=12\) GHz and \(\mathrm{f}_{1}=12.4\) GHz, respectively. Figure 11: Simulated and measured maximum gain and measured aperture efficiency of TA antenna. Figure 10: (**a**) Fabricated prototype with a support structure; (**b**) measurement setup in anechoic chamber. To evaluate the effects of the fabrication tolerances, several simulations have been performed. In particular, all the optimized cells have been slightly changed, by considering an increase of external radius values \(\Delta\)R\({}_{1}\) = 7.5 \(\upmu\)m and a decrease of internal radius values \(\Delta\)R\({}_{2}\) = \(-\)7.5 \(\upmu\)m, the obtained gain variation in broadside direction is \(\Delta\)G\({}_{80}\) = \(-\)0.5 dB. Moreover, the displacement of the focal distance F of the feed antenna along the z direction has been varied. For a variation of \(\Delta\)F = \(\pm\)4 mm, the maximum gain is reduced of G\({}_{80}\) = \(-\)0.3 dB and the main beam direction tilts of about \(\Delta\)\(\theta\) = \(-\)1\({}^{\circ}\). It is worth noting that, in the design, the substrates are considered perfectly adherent. Since in the prototype fabrication they were assembled with teflon screws, the influence of an air-gap with a thickness t\({}_{a}\) = 50 \(\upmu\)m between substrates in the unit cell has been investigated, obtaining a transmission coefficient variation \(\Delta\)S\({}_{2,1}\) = \(-\)0.12 dB and phase shifting variation of \(\Delta\)\(\phi\) = 1.3\({}^{\circ}\) with a gain variation in broadside direction of approximately \(\Delta\)G\({}_{80}\) = \(-\)0.6 dB.