## 3 Results  
The antenna was fabricated according to the optimized parameters listed in Table 1, illustrated in Figure 6. The reflection coefficient of the antenna was analyzed in two conditions, one was without integrating solar panel and another was integrating solar panel between antenna and ground plane, shown in Figure 7. The solar panel affected the antenna impedance of the antenna and shifted the resonant frequency by 3 MHz. The resonant frequency was tuned by optimizing its parameters. The proposed antenna achieved a \(-10\) dB impedance bandwidth of 6.0 MHz (447.5 MHz-453.5 MHz). The radiation characteristics of the proposed UHF antenna with the satellite structure were measured in the Satimo near-field measurement system. The measured radiation pattern in both the azimuth and elevation planes, along with the 3D pattern at 450 MHz is illustrated in Figure 8, where it can be observed that the antenna shows a nearly omnidirectional radiation pattern at the azimuth plane. According to the results in Figure 9, the total efficiency of the proposed UHF antenna at the resonance frequency was approximately 67.45% with 0.6 dB of realized gain, although the lossy nature of the solar cells degraded the antenna efficiency. Figure 5: Surface current distribution of the planner inverted F antenna (PIFA) antenna at 450 MHz; starting from the feed point, the travelling current forms a larger electrical path to achieve resonance at a lower frequency. The output power of the solar panel was measured using the solar simulator. The schematic layout of the measurement setup is depicted in Figure 10. At first, the solar panel was placed in the setup and the output power was measured. The output power measurement was conducted using a fixed load. Then the solar panel was placed between the antenna and the ground plane and the solar panel output power was measured. Both results are plotted in Figure 11a, which shows that more than 75% of the solar output was achieved compared with the open space solar output condition. The respective short-circuit current was also shown in the figure. Moreover, according to [18] the open circuit voltage and short circuit current had the open circuit voltage and the short circuit current was investigated by varying the antenna input power from 0.1 W to 0.5 W; this is plotted in Figure 11b. This investigation confirms that the antenna radiation power had no visible effect on the solar panel performance. Figure 6: Fabricated prototype of the proposed antenna integrated with the solar panel; the solar panel is placed in between the radiating patch and ground plane. Figure 7: Simulated and measured reflection coefficient of the proposed antenna. Reflection coefficients are measured with and without the solar panel and the measured \(-\)10 dB operating bandwidth is 447.5 MHz–453.5 MHz. Figure 8: Measured radiation pattern at 450 MHz (**a**) azimuth and elevation (**b**) 3D pattern showing omnidirectional radiation characteristics. Figure 10: Solar panel output power measurement setup. The components are: Solar-simulator, vector network analyzer (VNA), Multi-meter and the proposed Antenna. The output power measurement was conducted using a fixed load. Figure 9: Simulated and measured total efficiency and gain of the fabricated prototype; where 67.45% efficiency is achieved with 0.6 dB of realized gain. Random vibration and sine vibration tests of the proposed antenna integrated with nanosatellite structure were carried out to examine the stability of the antenna structure under vibration conditions. The test was performed in the Laboratory of Spacecraft Environment Interaction Engineering (LaSEINE), Kyushu Institute of Technology, Japan. The test setup is presented in Figure 12. No malfunctions occurred during excitation and after excitation. The antenna was in the exact position as it was before the vibration test.