# Design of Multi-Mode Antenna Array for Use in Next-Generation Mobile Handsets
## 8 Integration of a Compact MM-Wave Phased Array  
In this section, a new and miniaturized MM-Wave phased array 5G antenna with broad bandwidth is proposed to be incorporated in a shared board. The design details of the integrated phased array are illustrated in Figure 19a. It has a very compact size, with an overall size of \(\rm{W_{a}\times L_{a}=18\times 5\ mm^{2}}\), and it can be implemented in the same FR-4 laminate PCB with a thinner thickness of 0.8 mm. As shown, its configuration is composed of eight loop dipole resonators with pairs of directors arranged in a linear form. A discrete feeding port is applied separately for each antenna. The parameter values (in mm) are as follows: \(\rm{W_{a1}=2.8}\), \(\rm{W_{a2}=0.125}\), \(\rm{W_{a3}=0.15}\), \(\rm{W_{a4}=1.8}\), \(\rm{W_{a5}=0.4}\), \(\rm{W_{a6}=0.15}\), \(\rm{L_{a1}=1}\), \(\rm{L_{a2}=1.5}\), \(\rm{L_{a3}=0.2}\), \(\rm{d_{a}=0.125}\), \(\rm{d_{a1}=0.8}\), \(\rm{d_{a2}=1.3}\). The phased array is designed to work at 28 GHz--one of the promising 5G candidate bands at higher frequencies [82; 83]. However, due to the broad bandwidth characteristic, the proposed phased array is also capable of covering 26 and 30 GHz 5G bands [84; 85; 86]. Figure 19b plots the S-parameters (\(\rm{S_{11}-S_{41}}\)) of the phased array. As seen, the designed phased array provides a broad impedance bandwidth of 25-31 GHz with a central frequency of 28 GHz. Besides, less than a \(-15\) dB mutual coupling characteristic is obtained for the antenna elements. Figure 19c compares the maximum gains of the antenna element and the phased over the operation band. It is shown that the antenna element provides 4-5 dBi gain values over the operation frequency, whereas more than 12 dBi maximum gain is achieved for the designed array. The 3D beam steering functions of the array at 28 GHz for different angles are plotted in Figure 20a. The shapes and directions of the phased  
Figure 19: (**a**) Design details and configuration of the array, (**b**) its S-parameters, and (**c**) gain comparison of the array and the antenna element. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Component** & **Material** & **Permitivity** \\ \hline Screen & LCD film & 4.8 \\ Battery. Camera, Speaker & perfect electric conductor (PEC) & - \\ USB Connector & Brass (PEC) & \\ Button & Rubber & 3.5 \\ printed circuit board (PCB) & FR-4 & 4.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Characteristics of the smartphone components. array beams are determined by the relative phase amplitudes applied to each antenna element with discrete-feeding ports, as shown below [87]:  
\[\psi=2\pi\bigg{(}\frac{d}{\lambda}\bigg{)}sin\theta \tag{6}\]  
As shown, the designed phased array provides a good beam-steering function with end-fire radiation beams. As illustrated, the designed array exhibits high gain radiation beams with low sidelobes. The active reflection coefficients (ARCs) of the design for different scanning angles are illustrated in Figure 20b. As the radiation beam of the antenna is scanned, the amount of coupling between the radiation elements changes, meaning that the active reflection coefficient curve moves slightly [88]. However, as shown, the proposed phased array antenna exhibits sufficient performance and supports the target frequency bandwidth for different scanning angles. The radiation efficiency of the proposed array antenna is more than 75% in the operating bandwidth of all switching modes. Figure 20c plots the radiation and total efficiency levels of the array at scanning angles of 0, 30, and 60. It is shown that the proposed phased array offers quite good efficiency results. Figure 21 shows the possible placements and radiation beam-steering of the proposed phased array in the configuration of the smartphone board. It can be observed that the array can be easily integrated into a small area of the PCB and could provide full radiation coverage supporting different sides of the handset [89].