## 4 Experiment Results and Discussion  
To validate the simulated results, the prototypes of the 4 \(\times\) 1 patch array antennas using uniform and tapered power distributions and the 4 \(\times\) 1 patch array antenna using a tapered power distribution appended with two metallic plates at the tilting angle \(\theta\) = 70\({}^{\circ}\) and metallic plate length \(l_{\text{m}}\) = 50 mm were fabricated, as shown in Figure 9. A high-performance SMA connector (PSF-500-000, GigaLane Co., Ltd., Hwaseong, Korea) designed for applications up to 26.5 GHz, was used. A support structure made of acryl (\(\epsilon_{\text{r}}\) = 2.56) was designed and fabricated using the VLS 3.50 model laser cutting system (Universal Laser Systems, Scottsdale, AZ, USA), as shown in Figure 9c. The dimensions of the support structure are shown in Figure 9d. A 36 \(\upmu\)m-thick copper tape (1181, 3M Co., Ltd., Saint Paul, MN, USA) was used to make the two metallic plates. The simulated and measured results of the fabricated antennas are compared in Figure 10. An Anritsu 37397C vector network analyzer (Anritsu Co., Ltd., Morgan Hill, CA, USA) was used to measure input reflection coefficient and realized gain characteristics. For the 4 \(\times\) 1 patch array antenna using a uniform power distribution, the simulated and measured frequency bands for a VSWR less than two were 23.805 to 24.429 GHz (2.59%) and 23.851 to 24.840 GHz (4.06%), respectively, and were 23.836-24.402 GHz (2.35%) and 23.819-24.381 GHz (2.33%), respectively, for the 4 \(\times\) 1 patch array antenna using a tapered  
Figure 9: Photographs and dimensions of the fabricated antennas: (**a**) the 4 \(\times\) 1 array antenna using uniform power distribution, (**b**) the 4 \(\times\) 1 array antenna using tapered power distribution, (**c**) the 4 \(\times\) 1 array antenna using tapered power distribution with metallic plates, and (**d**) the dimensions of the acrylic support structure for the metallic plates. (All units are in millimeters). power distribution. Note that the measured frequency band for the 4 \(\times\) 1 patch array antenna using uniform power distribution moved toward a high frequency with a bandwidth increase, whereas the measured frequency band shifted toward a low frequency with a similar bandwidth. For the 4 \(\times\) 1 patch array antenna using a tapered power distribution appended with two metallic plates, the simulated and measured frequency bands for a VSWR less than two were 23.767 to 24.414 GHz (2.69%) and 23.725 to 24.365 GHz (2.66%), respectively, and, therefore, the measured frequency band shifted toward a low frequency with a similar bandwidth. For the 4 \(\times\) 1 patch array antenna using uniform power distribution, the simulated and measured realized gain in the 24.0 to 24.25 GHz band were 11.44 to 11.64 dBi and 10.3 to 10.5 dBi, respectively, with maximum gain decreasing by 1.14 dB. The simulated and measured realized gain in the 24.0 to 24.25 GHz band was 10.94 to 11.11 dBi and 9.7 to 9.8 dBi, respectively, for the 4 \(\times\) 1 patch array antenna using tapered power distribution, with maximum gain decreasing by 1.31 dB. For the 4 \(\times\) 1 patch array antenna using a tapered power distribution appended with two metallic plates, the simulated and measured realized gain in the 24.0 to 24.25 GHz band were 18.19 to 18.29 dBi and 16.7 to 16.8 dBi, respectively, with maximum gain decreasing by 1.49 dB. The measured radiation patterns of the fabricated antenna on the y-z and z-x planes at 24.125 GHz are compared with the simulated results in Figure 10c-h. The measured radiation patterns agreed quite well with the simulated results. For the 4 \(\times\) 1 patch array antenna using uniform power distribution, the simulated and measured sidelobe levels for the z-x plane were \(-\)13.4 dB and \(-\)9.5 dB, respectively, and the measured sidelobe level increased by 3.9 dB.