## 3 Analysis and Results Discussion of the Proposed 8-Elements AVA  
The prototype of the proposed eight-element AVA array is fabricated as shown in Figure 9. The simulated reflection coefficient, radiation pattern, gain and efficiency of the antenna are validated in the antenna measurement facility.  
The simulated and measured reflection coefficient (S11) are compared in Figure 10, and are found in close agreement. The S-parameter is below \(-10\) dB in the following three resonant bands, that is,  
1. [label=.]
2. Ku-Band (14.44-20.98 GHz)
3. 1 st mmW band (24.34-29 GHz)
4. 2 nd mmW band (33-40 GHz)  
The simulated and measured radiation pattern of the antenna in the two principal planes, that is, E-plane (XZ @ \(\phi\) = 90\({}^{\circ}\)) and H-plane (YZ @ \(\phi\) = 0\({}^{\circ}\)) are compared in Figure 11 at 15 GHz, 18 GHz, 28 GHz, and 38 GHz. The measured and simulated radiation patterns are found in close agreement. It is evident from the results that the main beam of the radiation pattern is oriented along \(\theta\) = 0\({}^{\circ}\) and 180\({}^{\circ}\). Also strong radiations are observed at other angles in this plane. In the H-plane, the main beam is aligned nearly at 90\({}^{\circ}\). For f = 15, 18, and 28 GHz, radiation pattern is somewhat Omni-directional in the third and fourth quadrants of the H-plane, however at f = 38 GHz strong radiation is observed in the third quadrant covering the angular range of \(\theta\) = \(-\)30\({}^{\circ}\) to 100\({}^{\circ}\). A major lobe with a sufficient gain (\(>\)5 dBi) occurs at \(\theta\) = \(-\)60\({}^{\circ}\) in this plane for f = 38 GHz.  
Figure 8: Transmission coefficients of eight elements AVA fed by separate ports.  
Figure 9: Fabricated antenna. (**a**) Front view. (**b**) Back view.  
Figure 11: Comparison of the simulated and measured radiation patterns of the proposed antenna.  
Figure 10: Comparison of simulated and measured S11 of the proposed antenna.  
The simulated and measured gain plots as function of frequency are shown in Figure 12. Measured gain values of the proposed design at 15 GHz, 18 GHz, 28 GHz, and 38 GHz are 10 dBi, 10.5 dBi, 11.5 dBi, and 10 dBi, respectively. The proposed antenna presents decent gain (>10 dBi) in the targeted frequency bands and hence due to this high-gain capability it can be considered as a suitable candidate for 5G and radar applications.  
To understand the insight operating mechanism of the proposed antenna at f = 15, 18, 28 and 38 GHz, the surface currents of the antenna are analyzed in Figure 13. It can be seen that the surface currents at 15 GHz and 18 GHz are concentrated at the center of lower part of the split leaf and spread along the edges. In contrast, the surface currents at 28 GHz are concentrated at the center of upper part of the split leaf and spread along the edges. While surface current are resides on the edges, as the frequency increased to 38 GHz. This concludes that lower part of the leaf is effective and generate radiation at 15 GHz and 18 GHz while upper part is the main contributor for radiation at 28 GHz and 38 GHz.  
The simulated and measured efficiencies are shown in Figure 14. Proposed 8-element AVA array radiates efficiently (>86%) in the stated frequency bands, due to the properly matched design on a less lossy substrate.  
Figure 12: Comparison of simulated and measured gain of the proposed antenna.  
Figure 13: Surface current plots of the proposed antenna. (**a**) 15 GHz. (**b**) 18 GHz. (**c**) 28 GHz. (**d**) 38 GHz.