## 4 Heterogeneous Substrate and Analysis
The top surface current distribution shown in Figure 4 will make the impact of changing the S1 parameter clearer. The S1 in Figure 5(a) is in accordance with the plan, showing the excellent surface current distribution caused by good coupling between Director 1 and Driven elements. The S1 parameter is substantially larger than the initial value in Figure 5(b), which leads to poor coupling between Driven and Director elements and a reduced surface current distribution. Figure 5: Comparison of with heterogeneous substrate and without heterogenous substrate in terms of frequency and gain. Figure 6: _Cont._  
A single radiating element with a width of '2W' is how the sides of the D1 elements behave. The S2 parameter can be positioned in a variety of ways to produce the largest possible effective aperture. The electrical width of the effective aperture grows as the S2 parameter increases, increasing the gain. The coupling between the D2 and D1 elements decreases when S2 grows too much, which causes gain to drop. The gap capacitance and the fringing capacitance should be adequate for the D2 element to acquire the required radiation if the S2 value is modest enough. The effects of changing the S2 parameter up or down are clearly seen in the surface current distribution shown in Figure 7,b. As previously stated, the gain improvement is caused by the S2 parameter, which widens the antenna's effective aperture. Director 1 has an effective width that is nearly twice as wide as its physical breadth. To obtain the smallest radiations required for resonance, the center of Director 2 may therefore be placed next to the center of Director 1. Therefore, it was found that raising S2 causes gains to continuously improve, and vice versa. Due to insufficient coupling capacitance, an excessive increase in the S2 parameter will cause yields to drop. Figure 6: The surface current distribution. Figure 7: _Cont._  
As shown in Figure 6a, the radiation is at its greatest because D2 elements are connected from the margins of the D1 component. This causes the effective aperture to have a wider electrical field, which increases gain. The antenna's electrical width is narrower in Figure 6b than in Figure 5a, which causes a weak surface current distribution and lower gain. The design's simulation results show an impedance bandwidth of 15.17% in a range of 10.72 GHz. In Figure 8, the S11 parameter is displayed. Figure 8: S\({}_{11}\) parameter of the simulated design. Figure 9: Radiation pattern of far field at 72 GHz. Figure 10 demonstrates the 2D far-field radiation behavior of gain at frequencies of 65, 66, 68, 70, 72, and 74 GHz, respectively. The angular width (3 dB) and main lobe magnitude and direction can be noticed in Figure 3:0 At 72 GHz, the angular width (3 dB) is \(36.8^{\circ}\), and the main lobe direction is at \(28^{\circ}\), whereas the maximum magnitude of the main lobe is \(11.8\) dB. Table 2 compares the previously designed antenna with homogenous substrate and the antenna intended in this work with the heterogeneous substrate. \begin{table}
\begin{tabular}{c c c c c c} \hline
**Results** & **Gain (dBi)** & **Directivity (dB)** & **Bandwidth (GHz)** & **\%Bandwidth** & **Efficiency (dB)** \\ \hline
[20] & 10.3 & 10.8 & 4.4 & 7.6 & \(-0.88\) \\ \hline Proposed model & 12 & 12 & \(11\) & 15.2 & \(-0.034\) \\ \hline \end{tabular}
\end{table} 
Table 2: Results comparison of current and previous design. Figure 10: Far-field representation of Polar plot at (**a**) 65 GHz, (**b**) 66 GHz, (**c**) 68 GHz, (**d**) 70 GHz, (**e**) 72 GHz, (**f**) 74 GHz. The millimeter-wave spectrum, which is anticipated to be used in the next generation of 5G technology, is where the band of the intended antenna is located. With regard to applications such as device-to-device communication, WLAN, and WPAN, the V-Band (50-75 GHz) of millimeter waves should be used (D-2-D).