# A Dual-Band Modified Franklin mm-Wave Antenna for 5G Wireless Applications
## 2 Antenna Design Approach  
### Proposed Antenna Configuration and Dimension Layout  
The final antenna or the proposed antenna with detailed optimized dimensions is shown in Figure 1. The antenna has a 3 \(\times\) 3 array-like structure, which consists of 9 patch elements, of which six of these patch elements have a dimension of P\({}_{\rm L}\)\(\times\) P\({}_{\rm W}\). Three of them have a dimension of (P\({}_{\rm L}\) + R) \(\times\) P\({}_{\rm W}\). Each row of these patch elements also has folded dipole elements that connect the row-wise patch elements. The antenna feeding network is provided to the last row of the patch elements. The ground plane consists of nine slots that are etched in a 3 \(\times\) 3 manner to provide the required response. The last cut in the first column of the array follows a slight misalignment to obtain the proper response with an appropriate gain required for proper operation. The detailed dimensions of the antenna are shown in Table 1. The antenna designed in this paper is based on the concept of [7; 11; 18; 20].  
The proposed modified Franklin array structure is based on a collinear array structure. A set of patches and stubs constitutes a collinear array structure. The modified Franklin array structure consists of 9 patch antennas arranged in a 3 \(\times\) 3 configuration, and in between each row of these patches contains stubs that have been changed to symmetrically folded dipole like structures, as illustrated in Figure 1. These 9 patch antennas and folded dipole-like structures arranged in a 3 \(\times\) 3 array manner are connected to a feeding network that has been modified into a folded dipole like structure and connected from the last row of patch antennas and folded dipole like structures.  
The patch antennas are of dimensions P\({}_{\rm L}\)\(\times\) P\({}_{\rm W}\). The six patch antennas in the second and third row of the array follow these dimensions. The first row of patch antennas has an incremental length R added to it. The dimensions of the patch antennas are designed based on \(\lambda\)/2 of the second resonant frequency. Similarly, in an arrangement similar to the 3 \(\times\) 3 arrangement of patch elements, modifications are made to the ground in a 3 \(\times\) 3 manner to the original design such that the desirable dual-band operation of the antenna is achieved.  
HFSS, or High-Frequency Structure Simulator software, is used in the modeling, simulation, and analysis, as well as for the numerical evaluation of the antenna design. The substrate used had a height (h) of 0.8 mm, and a metallic ground was used at the bottom.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Symbol** & **Parameters** & **(mm)** \\ \hline P\({}_{\text{L}}\) & Patch element length & 4.34 \\ P\({}_{\text{W}}\) & Patch element width & 4.3 \\ R & Patch element length extension for the first row & 1.0 \\ J & Spacing between the centers of patch elements in a row & 8.01 \\ F\({}_{\text{L}}\) & Folded dipole length & 1.4 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Optimized dimensions of the final proposed antenna.  
Figure 1: Final antenna (**a**) top view and (**b**) bottom view.