# Integrated Module Antenna for Automotive UWB Application
## 2 Proposed Antenna Design
### Pattern Improvements with Modified Ground Stubs and Parasitic Radiators  
In order to compensate the influence of the shared ground of the patch array, the additional ground stubs are applied on the 3 rd layer. The improvements of the radiation pattern by adding the stubs are provided in stepwise in Table 1.  
When stub 1 is applied in step 2, the phase difference of the current between the monopole and edge of the module ground close to stub 1 is changed from 160\({}^{\circ}\) to 90\({}^{\circ}\). At 6.5 GHz, the beamwidth of the monopole is expanded from 86.9\({}^{\circ}\) to 124\({}^{\circ}\), and at 8.0 GHz, it slightly decreased from 119\({}^{\circ}\) to 115\({}^{\circ}\). The entire shape of the radiation pattern is broadened and the fluctuation is reduced. In addition, stub 1 is applied to the patch array with 70\({}^{\circ}\) of phase difference. The beamwidth of the patch array is also expanded from 75.6\({}^{\circ}\) to 85.1\({}^{\circ}\) in the xz-plane. However, the beamwidths of the monopole and patch array are not sufficient for the localization and the detection sensor. In step 3, when stub 2 is applied, the phase  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Step 1 (Prototype)** & **Step 2** & **Step 3** \\ \hline \hline
**Radiation Pattern of Monopole (yz-Plane)** & **Radiation Pattern of Monopole (yz-Plane)** \\ \hline \hline
**Radiation Pattern of Patch Array (xz-Plane)** & **Radiation Pattern of Patch Array (xz-Plane)** \\ \hline \hline  
difference of the current between the monopole and stub 2 is 180\({}^{\circ}\). Because of this, the beamwidth of the monopole is expanded from 124\({}^{\circ}\) to 146\({}^{\circ}\) at 6.5 GHz. At 8.0 GHz, the beamwidth is slightly reduced from 115\({}^{\circ}\) to 111\({}^{\circ}\). Meanwhile, stub 2 has no discernible effect on the patch array, and the beamwidth is maintained at 85.5\({}^{\circ}\). Additional stubs are added in order to expand the beamwidth of the patch array and monopole even further. Step-by-step descriptions of the effects of enhancing the radiation pattern by adding additional stubs are provided in Table 2.  
In the step 4, the current path on the stub 1 is extended when the stub 3 is applied. Then the phase difference of the current between the patch array and the stub 1 is changed from 70\({}^{\circ}\) to 90\({}^{\circ}\) and the beamwidth of the patch array is expanded from 85.5\({}^{\circ}\) to 95.7\({}^{\circ}\) in the xz-plane. However, the gain is reduced under the 5 dBi. Meanwhile, the beamwidths of the monopole at 6.5 GHz and 8.0 GHz are still maintained as the beamwidths of step 3. In step 5, the stub 4 with a phase difference of 180\({}^{\circ}\) from the monopole is added, and the  
\begin{table}
\begin{tabular}{c c  
stub 5 is added so that the phase difference between the ground of the monopole and the stub 2 is 180\({}^{\circ}\). Then beamwidth of the monopole at 6.5 GHz and 8.0 GHz are expanded from 146\({}^{\circ}\) to 175\({}^{\circ}\) and from 111\({}^{\circ}\) to 119\({}^{\circ}\) when the stub 4 and 5 is applied. However, patch array has no notable change and the beamwidth is maintained at 95.7\({}^{\circ}\). To compensate the gain reduction of the patch array, parasitic radiators are applied on the 1 st layer. As shown in step 6 of Table 3, the parasitic radiator 1 is located between patches. The parasitic radiator 2 is located at the top of the patch array and is connected with ground through the metal via, as shown in step 7 of Table 3. The effects of improving the radiation pattern by adding the radiators are summarized in Table 3 step by step. Due to the parasitic radiators, the gain of the patch array increased from 4.31 to 4.91 dBi, whereas the beamwidth in the xz-plane remained greater than 90\({}^{\circ}\). The parasitic radiators were electrically separated from the patch array, so these did not increase the  
\begin{table}
\begin{tabular}{c c  
The proposed antenna shows 176\({}^{\circ}\) and 118\({}^{\circ}\) beamwidth in yz-plane at 6.5 GHz and 8.0 GHz when the monopole excited.