## 2 Proposed Integrated Design
### Mid-Band (4G LTE and Lower 5G) MIMO Configuration  
A systematic procedure was followed for the design of the low frequency MIMO configuration. The reported optimized antenna was designed after five evolution stages. In the first stage, standard mathematical Equations (1)-(3) were used for the design of the initial microstrip-fed rectangular patch antenna with complete ground [24]. The S11 parameter for the same stage is reported in Figure 2 as Step-1. It can be observed that the antenna operates as per \(-10\) dB standard, from 3.4 to 6 GHz. However, in order to cover the mentioned applications band, horizontal slits were added into the design, referred to as Stage-2. The dimensions for the slits were optimized using the empirical parametric analysis. The S11 parameter for this stage is reported in Figure 2 as Step-2. \[W_{p}=\frac{c}{2f_{c}\sqrt{\frac{\varepsilon_{p}+1}{2}}} \tag{1}\]  
\[L_{p}=\frac{c}{2f_{o}\sqrt{\varepsilon_{reff}}}-2\Delta L \tag{2}\]  
where,  
\[\Delta\text{L}=0.421\;\text{h}\frac{(\varepsilon_{\text{reff}}+0.3)\left( \frac{\text{W}_{s}}{\text{H}}+0.264\right)}{(\varepsilon_{\text{reff}}-0.258) \left(\frac{\text{W}_{s}}{\text{H}}+0.8\right)}. \tag{3}\] \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Name** & **Value (mm)** & **Name** & **Value (mm)** \\ \hline \multicolumn{4}{c}{**Mid-Band Single and MIMO (4G LTE and Lower 5G) antenna**} \\ \hline Lf & 7.25 & Wslit & 2.2 \\ Warr & 35 & Wf & 4.85 \\ Larr & 17.86 & Ltf & 6.44 \\ Lslit2 & 4.5 & Wslit2 & 0.61 \\ Wg & 41.16 & Lg & 9.25 \\ \hline \multicolumn{4}{c}{**High-Band Single and MIMO (5G mmWave band) antenna**} \\ \hline Wpm & 5 & Lfm & 2 \\ Lpm & 7.6 & Wfm & 5.25 \\ TFm & 3 & Lpt & 2.6 \\ SW & 0.8 & SL & 0.5 \\ Wmg & 10.25 & Lmg & 10 \\ Gsw & 1.99 & gsl & 3 \\ \hline \multicolumn{4}{c}{**Integrated MIMO antenna**} \\ \hline Ws & 71.8 & mmW & 56.6 \\ Ls & 151 & mmL & 45 \\ Dist\_MIMO & 87.82 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Dimensions of the proposed design. Afterwards, an additional pair of slits were introduced in the upper half part of the design, the position and dimension for the slit were optimized by the use of parametric analysis. The S11 parameter for the modified design is reported in Figure 2 as Step-3. Furthermore, in order to increase the performance of the design, different transformations were applied to the design. After the analysis, it was found that bending in the upper and lower half portion provides good results in terms of better VSWR and matching. The bending was explored at different angles and, after the analysis, it was found that bending the value of 8 generates the best results. The S11 parameter for the fourth and the fifth stage is reported in Figure 2 as Step-4 and Step-5. After the design of the novel single element, an array for the final antenna design was explored for further improving the gain and bandwidth. The S-parameter for this stage is reported in Figure 3a. Finally, a two-element MIMO configuration for the mid-band applications was designed by placing the final designed array at the top and bottom of the sheet. The location was selected by keeping in view the place of other electronic components for the standard devices. The detailed annotation and values for the different dimensions for the single, array and MIMO antenna designed for the mid-band are reported in Figure 3 and Table 1.  
The S-parameters for the single-element array and MIMO configuration are reported in Figure 4. It can be noted that the designed single element resonates from 2.83 to 4.03 GHz, therefore covering a \(-\)10 dB bandwidth of 1.2 GHz (covering lower 5G and 4G LTE bands). However, as a result of gain-bandwidth trade-off, gain in the entire band is not high; therefore, an array configuration for the design was explored. The array was optimized by the use of empirical parametric study analysis.