## 5 Results  
The prototype antenna was measured in an anechoic chamber using the multi-probe system Starlab and other microwave facilities at MVG Italia ([[https://www.mvg-world.com/en](https://www.mvg-world.com/en)]([https://www.mvg-world.com/en](https://www.mvg-world.com/en)) (5 October 2022), as shown in Figure 8.  
The simulated and experimental results (in terms of return loss and H/V isolation) of the proposed antennae are compared in Figure 9. The simulations shown in the Figure 9  
Figure 8: A picture of MVG Starlab measurement setup. The prototype antenna is over the central mast.  
Figure 7: Different view of realized prototype.  
also take into account the effect of the PLA supports used as a framework for the antenna. The bandwidth is almost equal to the simulation, having a slight shift upwards of 100 MHz (2.91-4.81 GHz). Meanwhile, the measured results show that the H port achieves about 49% (2.89-4.75 GHz) and the V port achieves about 48% (2.88-4.69 GHz) of the impedance bandwidth at a return loss greater than 10 dB. The measured H/V isolation is almost always greater than 30 dB, except in the initial part of the band below 3 GHz, where it reaches 25 dB.  
Additionally, the co-polar and cross-polar realized gain of the proposed antenna are measured and simulated, and results are shown in Figure 10. Simulated co-polar gain varies between 8.7 and 10.4 dBi (9.8 and 10.8 dBi), with 1.7 dB (1 dB) variation in the whole bandwidth for the H port (V port). Within the operating frequency range, measured results show that the co-polar gain of the proposed antenna is between 7 and 10.3 dBi (8.1 and 10.9 dBi), with 3.3 dB (2.8 dB) variation for the H port (V port). Simulation of cross-polar gain is always less of \(-\)30 dBi for the H port; it is slightly higher (less than \(-\)23 dBi) for the V polarization within the operating band. The cross-polar gain difference between dual polarization is due to the position of the slot relative to the patch. In particular, while the slot of the H port is centered with respect to the \(D1\) direction, the slot of the V port has an offset equal to \(V_{OFFSET}\) with respect to the D2 direction. Measured results show that the cross-polar gain of the proposed antenna is always less than \(-\)13 dBi for both polarizations. A comparison between simulated and measured realized gain and efficiency for both polarizations is shown in Figure 11. Within the operating frequency range, the measured efficiency is between 0.85-0.98 (0.78-0.997) for the H port (V port). The gain differences between the measured and simulated results come, probably, from the possible loss of symmetry of antenna geometry because of manufacturing imperfection and measurement tolerance. In addition, PLA losses, which are not perfectly known, could adversely affect the gain. Furthermore, we substituted honeycomb with air in the realized prototype. Figure 12 shows the simulated and measured results of the co-polar gain for three different frequency values--3 GHz, 3.6, and 4.5 GHz--and for H and V polarization. Good agreement between simulation and measurement results was achieved.  
Figure 9: Scaled prototype: simulations vs. measurements. Return loss on the (**left**) and H/V isolation on the (**right**).  
Figure 11: Scaled prototype: comparison between measurement and simulation in term of realized co-polar gain and total efficiency for both H/V polarizations.  
Figure 10: Scaled prototype: comparison between measurement and simulation in term of co-polar and dorsal-polar gain for both H/V polarizations.