# Low-Profile Dual-Band Reflector Antenna for High-Frequency Applications
## 3 Measurement Verifications  
To verify the dual-band antenna performance, a prototype was manufactured and measured. Considering that the antenna is composed of metal and linear dielectric materials, excluding ferrites, it meets the fundamental scaling principles versus frequencies. Meanwhile, since the anechoic chamber corresponding to the interesting frequency bands in our university was unavailable, it was difficult to accurately measure the radiation patterns at terahertz frequencies. Therefore, the dual-band MMW/THz antenna was scaled to Ku/E-band, and Ku-band performance was accurately measured. The higher band performance has not been experimentally verified, but the simulated results show that the dual-band antenna in the higher band can achieve high gain and high radiation efficiency. The scaled antenna has an aperture dimension of 300 \(\times\) 300 \(\times\) 93 mm\({}^{3}\), as shown in Figure 10a,b. Meanwhile, the composite feed and SRA are shown in Figure 10c,d. The machining process was employed to fabricate all parts of the antenna except the SRA, and the Printed Circuit Board (PCB) technique was utilized to manufacture the SRA. Because the reflector was assembled from several parts using screws and glue, it was difficult to precisely take account into the errors of assembly when the model was simulated. \begin{table}
\begin{tabular}{c c} \hline \hline
**Factors** & **Gain (Efficiency)** \\ \hline Maximum directivity (dB) & 33.70 (100\%) \\ Feed mismatch loss (dB) & 0.46 (90.5\%) \\ Dielectric loss (dB) & 0.066 (89.1\%) \\ Spillover loss (dB) & 0.46 (80.2\%) \\ Taper loss (dB) & 1.31 (59.3\%) \\ Shade loss (dB) & 0.09 (58.2\%) \\ Calculated gain (dB) & 31.4 (58.2\%) \\ Simulated gain (dB) & 31.4 (59.0\%) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Loss budgets and aperture efficiency at _f_l. Figure 9: In the condition that the \(\Delta\Phi\) is 90\({}^{\circ}\): (**a**) desired compensation phase of SRA and (**b**) radiation patterns at _f_l. The simulated and measured reflection coefficients of the scaled feed in the Ku band are shown in Figure 11. The Ku-band performance of the scaled prototype can represent the low-band performance of the proposed antenna. There are slight differences between the simulated and measured reflection coefficients, mainly due to fabrication tolerance and assembly misalignment. The measured reflection coefficients are below \(-15\) dB within the desired frequency band of 14.7\(-\)16.2 GHz. The gain of the manufactured antenna is shown in Figure 12a. As can be seen, the measured gains are higher than 29.9 dBi and the measured total efficiencies are better than 43% within the frequency band of 14.7\(-\)16.2 GHz. Meanwhile, the measured gain results  
Figure 11: Simulated and measured lower-band reflection coefficients of the manufactured composite feed. Figure 10: Photographs of the manufactured reflector antenna: (**a**) Top view and (**b**) 3D view of dual-band reflector antenna. (**c**) The SRA. (**d**) The composite feed. show that the manufactured dual-band reflector antenna has a gain variation of less than 2 dB from 14.7 GHz to 16.2 GHz. The measured peak gain is 31.4 dBi, indicating an antenna aperture efficiency of 60.2% at 15.2 GHz, as shown in Figure 12b. Thus, the proposed dual-band reflector antenna can achieve high aperture efficiency and high gain with a low F/D of about 0.2. Moreover, the difference between the measured and simulated gains is less than 1 dB in the 14.7-16.2 GHz band. Figure 13 shows the comparison of simulated and measured normalized Co-pol and Cr-pol gain patterns at 15.4 GHz. As shown in Figure 13, the measured first sidelobe levels (SLLs) are below \(-\)10 dB in both the E-/H-planes. In terms of Co-pol, the measured main beam and first SLLs show good agreement with the simulated results in both the E-/H-planes. Additionally, the Cr-pol level of the measured results is below \(-\)25 dB, which is higher than the simulated results.