# The Uses of a Dual-Band Corrugated Circularly Polarized Horn Antenna for 5G Systems
## 4 Antenna Manufacturing and Experimental Measurement  
The corrugated circularly polarization horn antenna is shown in Figure 15. The antenna size is 160 mm \(\times\) 43 mm \(\times\) 43 mm. The antenna is composed of four different components. The middle part is a circularly polarized converter, and the corrugated structure is on the right side of the photo. For the middle parts, we proposed that a reconfigurable ridge be used to optimize axial ratio by using a different depth of ridge inside the waveguide. Figure 16a shows an NSI-700S-360 antenna chamber [16]. Its measurement coordinates are shown in Figure 16b. The simulation and measurement of return loss results are shown in Figure 17. The results show consistency in simulation and measurement. Axial ratio measurement results are shown in Figure 18. The measurement results show AR < 4.5 dB on low band and <5.1 dB on high band. The difference in simulation and measurement comes from the deviation in the manufacturing process. In an optimized process, it is found that a 0.1 mm variation in ridge size will cause 1 dB of fluctuation in the axial ratio. Thus, accuracy in manufacturing the ridge is very important for this horn antenna.  
Figure 14: Simulation result of 2D gain pattern on YZ Cut, (**a**) Low band (29 GHz) and (**b**) High band (39 GHz).  
Figure 15: Photograph of corrugated horn antenna sample.  
The measurement radiation pattern is shown in Figure 19. To attain the best beam width, 26.5 GHz and 36 GHz were selected to compare with the simulation data. The radiation pattern at 26.5 GHz shows a peak gain of 6.16 dBi and 5.78 dBi in two different cut planes, and antenna beam widths of 95 degrees and 105 degrees, respectively. The radiation pattern at 36 GHz shows peak gains of 8.74 dBi and 8.78 dBi, and antenna beam widths of 105 degrees, respectively. The radiation pattern at 36 GHz shows peak gains of 8.  
widths of 77 degrees and 75 degrees, respectively. The detailed beam width results for each frequency are listed in Table 3. The beam width ranges from 94 to 105 degrees on low band, and 60 to 77 degrees on high band. The low band beam width performance is better than the high band beam width for this design.  
Figure 20a shows a 3D simulation pattern of the antenna, and is compared to Figure 20b which was a 3D measurement pattern. The result shows the same shape as the antenna pattern. Figure 20c,d show equal performance at the 39 GHz point. Due to the reconfigurable ridge, this antenna has the capacity to optimize any band by using the tuning ridge. Figure 21 shows antenna radiation efficiency; the efficiency is about 85% to 95% on both bands. The frequency graph in Figure 22b indicates that the antenna has great axial ratio performance (AR < 3.1 dB) on the high band by pushing 0.2 mm inside the waveguide. However, this movement causes the deterioration of the low band axial ratio. This performance is reversed by pulling the ridge. This application will lead to another reconfigured design and is a future project for study.  
Figure 19: (**a**) Horn antenna gain measurement for 3 dB beam width (26.5 GHz, XZ-cut); beam width \(\sim\)97 degrees, (**b**) horn antenna gain measurement for 3 dB beam width (26.5 GHz, YZ-cut); beam width \(\sim\)105 degrees, (**c**) horn antenna gain measurement for 3 dB beam width (36.0 GHz, XZ-cut); beam width \(\sim\)77 degrees, (**d**) horn antenna gain measurement for 3 dB beam width (36.0 GHz, YZ-cut); beam width \(\sim\)75 degrees.  
Figure 20: 3D radiation pattern, (**a**) simulation (28 GHz), (**b**) measurement (28 GHz), (**c**) simulation (39 GHz), and (**d**) measurement (39 GHz).  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**3 dB Beam width** & **XZ-Cut (Degrees)** & **YZ-Cut (Degrees)** \\ \hline  
\hline \end{tabular}
\end{table}
Table 3: Maximum scan angle with different antenna spacing.