# A Sub-6 GHz MIMO Antenna Array for 5G Wireless Terminals
## 3 Results and Discussion  
The results obtained through simulation and measurements for the proposed corporate array depicted in Figure 5 are analyzed in this section. In Figure 7, the measurement setup is shown for the proposed corporate array results analysis. As shown in Figure 8, the reflection coefficient obtained for the corporate feed array is showing resonance at the desired band of 5.57 GHz with a magnitude of 25 dB. In case of corporate feed structure, the arrangement of elements is done such that--in terms of spacing between the elements  
Figure 5: Corporate feed sub-6 GHz array. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Value (mm)** & **Parameter** & **Value (mm)** \\ \hline W & 165 & L & 235 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Design parameters of MIMO array antenna. Figure 6: Corporate feed array MIMO configuration. the coupling among them should be negligible. The bandwidth covered by the proposed antenna array ranges from 5.54 to 5.59 GHz. The measured reflection coefficient follows the simulated one quite efficiently, with an improvement in the magnitude level. Furthermore, a 3 dB offset is observed between the simulated and measured reflection coefficient due to the losses by connectors. The minor shift in the frequency observed is due to fabrication tolerances. The VSWR is also below 2 for the operating bandwidth while at the central frequency, the value of it is observed to be 1.12, which shows that there is minimum reflection of the transmitted power from the radiating structure to the feed, as shown in Figure 9.  
Figure 8: Corporate feed array reflection coefficient. Figure 7: Proposed antenna array under testing: (**a**) measuring reflection coefficient and (**b**) radiation measurements inside the anechoic chamber. The radiation pattern is highly directive, with a gain of 12.4 dB as shown in Figure 10. It can also be seen that the side lobe level is highly reduced in this type of array structure. According to the 0-degree plane of radiation, the side lobe level is \(-17.1\) dB, which is quite satisfactory for 5G communication, and the main lobe direction is towards 0 degree, while the magnitude of the main lobe is found to be 12.6 dB. The angular width (3-dB beamwidth) is achieved at 22 degrees. However, in the 90-degree plane of radiation, the main lobe direction is along a 2-degree angle with a side lobe level of \(-17.1\) dB. The angular width (3-dB beamwidth) in this plane is 82.1 degrees, and the main lobe magnitude is 12.6 dB. Furthermore, the back lobe level in this plane is highly reduced, making the antenna perfect for the 5G communication environment. The measured results follow the simulated with a quite good coherence due to the better fabrication and measurement setup calibration. Figure 10: Corporate feed array gain pattern: (**a**) _E_-plane; (**b**) _H_-plane. Figure 9: Corporate feed array VSWR. The 3D gain pattern further helps to understand the above 2D gain pattern, as shown in Figure 11a using the Computer Simulation Technology (CST) software. The radiation and total efficiency within the operating bandwidth are 98.2% and 85.1%, respectively. The current distribution for the corporate feed structure is observed in Figure 11b, which uses the Computer Simulation Technology (CST) software to show that the current is mostly concentrated along the edges of the circular-shaped patch, and feedline while the current is negligible between the patches; this proves that the coupling among the elements is minimized by employing the corporate feeding technique. Thus, unwanted resonances are avoided in the return loss of the proposed antenna array, and a high gain is achieved with the high efficiency. Moreover, the current distribution in Figure 11b of the whole array ensures that the power distribution is equal to each antenna element. The distribution of the electric (E) and magnetic field (H) are shown in Figure 11c and Figure 11d, respectively.