# Study of Mesh Pattern for Optically Transparent Flexible Antenna with Feedline
## 3 Meshed Feedline and Antenna
### Meshed Antenna  
The antenna in Figure 8a will be compared for the solid antenna, square-meshed antenna, and diamond-meshed antenna at 2.4 GHz. Antenna with meshed feedline in Figure 8b will be compared. First, we analyzed the case of applying the mesh only to the antenna. In the case of a square-meshed antenna in Figure 9a, the peak realized gain decreases inversely as the size of the open space increases from 0.8 to 2.8 mm at fixed \(w_{s}\) = 0.14 mm. In Figure 9b, as the mesh width increases from 0.08 to 0.25 mm at fixed \(g_{s}\) = 1.5 mm, the gain of the antenna also increases proportionally. Solid antenna has peak realized gain 3.9 dB, but both have lower values in Figures 9 and 10. In the case of an antenna having the same operating principle, since the effective area of the antenna is proportional to the gain of the antenna, the OT and the gain of the antenna are opposite to each other. Similar to a square-meshed antenna, depending on the transparency, Figure 10a shows a relationship inversely proportional to the peak realized gain when \(g_{d,\,hor}\), and \(g_{d,\,ver}\) vary from 0.6 to 1.8 mm at fixed \(w_{d}\) = 0.14 mm and Figure 10b shows a proportional relationship when \(w_{d}\) varies from 0.1 to 0.42 mm at fixed \(g_{d,\,hor}\), and \(g_{d,\,ver}\) = 1.5 mm. It can be seen that the input impedance of the antenna to which the mesh is applied is hardly unaffected and the meshed antenna and the solid antenna are matched equally well in Figure 11. A simulated and measured 2-d radiation pattern of antennas without meshed feedline was compared in Figure 12. The square-meshed antenna and diamond-meshed antenna were manufactured with the specifications when the transparency was 82%. The solid antenna has a peak realized gain of 3.9 dB, the square-meshed antenna has 3.65 dB, and the diamond-meshed antenna has 3.64 dB. It was confirmed that the effective area of the antenna has a small effect on the gain regardless of the pattern of the meshed antenna, and that all three antennas operate with a similar surface current distribution in Figure 13.  
Figure 6: Effect of diamond mesh on loss factor: (**a**) length of the open space, \(g_{d,\,hor}\), \(g_{d,\,ver}\); (**b**) mesh width, \(w_{d}\). Figure 7: Simulated and measured s-parameter of solid feedline and diamond-meshed feedline. Figure 8: Meshed antenna: (**a**) square-meshed antenna without meshed feedline; (**b**) diamond-meshed antenna with meshed feedline. Figure 10: Effect of diamond mesh on peak realized gain: (**a**) length of the open space, \(g_{d,\;hor}\), \(S_{d,\;ver}\); (**b**) mesh width, \(w_{d}\). Figure 9: Effect of square mesh on peak realized gain: (**a**) length of the open space, \(g_{s}\); (**b**) mesh width, \(w_{s}\). Figure 11: Simulated and measured reflection coefficients (\(S_{11}\)) of the solid antenna, and the meshed antenna. Figure 12: Simulated and measured 2-d radiation pattern of antennas without meshed feedline: (**a**) E-plane; (**b**) H-plane. Figure 12.0 Surface current distribution of antennas w/o meshed feedline: (**a**) solid antenna; (**b**) square meshed antenna; (**c**) diamond meshed antenna. Finally, square mesh and diamond mesh were applied to antenna and feedline to have OT 85%. The meshed antenna to which the meshes were applied was compared with the solid antenna in Figure 12.1 Solid antenna, square-meshed antenna, and diamond-meshed antenna have 3.9 dB, 3.56 dB, and 3.6 dB, respectively, and it has been confirmed that they work well without distortion of the radiation pattern. Even with 85% transparency, the meshed antenna has no problem except for a gain difference of about 0.4 dB. In order to have OT 85%, a square meshed antenna was manufactured with the specifications of \(g_{s}=1.5\) mm, and \(w_{s}=0.12\) mm, and in the case of a diamond meshed antenna, \(g_{d,\;hor}\), and \(g_{d,\;ver}=1.5\) mm, and \(w_{d}=0.18\) mm. When two types of mesh are used as micro metal mesh film, it is advantageous in terms of process because diamond mesh can achieve higher transparency with the same mesh width [22].