## 3 Results and Discussion  
The designed device has been manufactured, and the resulting prototype is shown in Figure 2. Just two pieces of the substrate are needed: one for the microstrip layer and another for the patch, apart from a short metallic rod to fasten both layers. The manufacturing process is quite simple and can be completed with standard PCB operations, such as drilling, cutting, milling, plating, and soldering. The hole for the rod is drilled into both substrate pieces. Then, the microstrip layer is plated to metalize the hole. Afterward, the microstrip line is printed, and the final layer is cut. On the other hand, after drilling the patch layer, it is directly cut and completely plated. Next, the rod is cut to the desired length, and it is tin-soldered to the patch. Finally, the rod has to be carefully soldered to the microstrip layer. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \(l_{ms}\) & \(w_{ms}\) & \(h_{ms}\) & \(d_{rad}\) & \(pad_{ms}\) \\
40 & 1.784 & 0.813 & 3 & 2 \\ \(L_{s}\) & \(W_{s}\) & \(pad_{gr}\) & \(gap\) & \(h_{air}\) \\
120 & 110 & 2 & 1 & 8.13 \\ \(\Delta L\) & \(L_{p}\) & \(W_{p}\) & \(\Delta x\) & \(h_{p}\) \\
4.936 & 52.586 & 62.457 & 8.862 & 0.866 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Optimum dimensions (in mm) for the floating patch device. The prototype has been measured with a vector network analyzer (Agilent N5230C) to characterize the \(S_{11}\) parameter. The result is shown in Figure 3, which compares the measurement to the simulation. It reflects practically a total match between the simulated device and the manufactured prototype; the measured return loss is 30 dB at 2.4 GHz with a measured bandwidth of 10.41% around the resonance frequency. This fulfills one of the goals of achieving a high bandwidth for the patch antenna by using the air as a dielectric and a through-wire feed. The radiation of the prototype patch antenna has been also measured in an anechoic chamber with the technique of the reference antenna (QRH500, in this case), as can be seen in Figure 4. With the data acquired in this measurement procedure, the antenna can be completely characterized. Figure 3: Comparison of the measured and simulated parameter \(S_{11}\). Figure 2: Manufactured prototype; top and frontal views with a reference scale. The measured radiation pattern is shown in Figure 5, whose XZ (\(\phi=0^{\circ}\)), YZ (\(\phi=90^{\circ}\)), and XY (\(\theta=90^{\circ}\)) plane cuts are included in Figure 6. The obtained patterns are typical of a patch antenna. The measured directivity at the resonance frequency is 9.94 dBi, with a measured gain of 9.63 dBi, which gives a radiation efficiency of 96.41% and a total efficiency of 93.08%. The maximum direction of the radiation is \(\theta=2^{\circ}\) and \(\phi=224^{\circ}\), whereas the \(-3\) dB beamwidth is \(52^{\circ}\) for plane YZ and \(60^{\circ}\) for the XZ. Moreover, a good cross-polar rejection is obtained, with 67 dB for the polarization ellipse axial ratio. These results fit almost perfectly with the simulations and reveal, as intended, the simultaneous high-performance indexes of the return loss, bandwidth, beamwidth, gain, and efficiency. c  
Despite the quite easy manufacturing process for this antenna, some inherent fabrication errors may occur. A yield analysis has been performed to check the endurance and repeatability of the proposed prototype and its manufacturing. It has been considered that errors may appear in the most critical operations: the milling pads and gap for the rod as well as the drilling position for the rod in the patch and the cutting process for the size of the patch. The selected criteria to mark a device as acceptable are that \(S_{11}<-10\) dB at a minimum bandwidth of 10% around the resonance frequency. Taking into account that the tolerance of the laser cuts used is 2 microns, the analysis indicates that, even for high  
Figure 4: Measurement of the prototype in an anechoic chamber. Figure 5: 3D representation of measured electric field radiation.