# The Design and Implementation of a Phased Antenna Array System for LEO Satellite Communications
## 6 Performance Evaluation  
The measuring radiation pattern setup of the phased antenna array contained the emission part and the reception part. The phased antenna array represented the AUT (Array Under Test) and was installed in reception mode. A Yagi-Uda antenna was used in transmit mode as a test antenna for the AUT. Figure 12: The phase shifts achieved by the four-phase shifters (PS1–PS4) are to be implemented in the phased antenna array. The measurements were performed at a frequency of 435 MHz. Figure 13: Close-up view of the phase shifters control module, splitter/combiner, phase shifters and USB programming interface, integrated on the same PCB. As can be seen in Figure 14, for this antenna, a fixing system was adapted on a tripod with various mechanical adjustment facilities so that the test antenna could be fixed in various positions relative to the phased antenna array concerning height, axis tilt, and rotation around the tripod axis. An Agilent N5182A (MXG Vector Signal Generator) RF generator was configured at a frequency of 436.5 MHz and used as a sinusoidal signal generator, amplitude modulated with a 1 KHz sinusoidal signal. A low-loss RG058 transmission line with 50 Ohms impedance was used between the RF generator and the Yagi-Uda antenna. During the experimental measurements, the generator was adjusted to the output power of \(-2.3\) dBm, and the RG058 transmission line was approximately 15 m long. Consequently, the power of the Yagi-Uda antenna feed signal was approximately \(-7.3\) dBm. The ground station receivers can usually detect signals with an MDS level (Minimum Discernible Signal) between approximately \(-95\) dBm and \(-138\) dBm [40]. According to the simulation results, the proposed phased antenna array has a high gain, approximately between 11.55 dBi and 11.97 dBi, for different main radiation lobe orientation angles. These results demonstrate that the developed array system is suitable for implementation in LEO satellite reception systems. In Figure 14, it can be seen that the Yagi-Uda test antenna was positioned for radiation pattern measurements corresponding to approximately \(42^{\circ}\) elevation, so its axis was along the Ox axis of the phased antenna array under test. This led to a separation of about 1.5 m between the center of the array's ground plane and the Yagi-Uda antenna tip. That was considered as the axis that passes through the center of the ground plane of the array and parallel to the imaginary lines that join elements 1 and 2, respectively, 3 and 4. The positions of the array elements, thus numbered, are shown in the images of experimental results on the radiation patterns revealed in Figure 15, where the phased antenna array system was symbolized by a circle, and its elements were numbered from 1 to 4. To obtain the phased antenna array radiation patterns, the Lab-Volt laboratory equipment was used, which included the antenna positioner and the data acquisition interface. The signal received by the antenna array was amplified by the input amplifier included in the antenna positioner and then sent to the data acquisition interface. Figure 14: The measuring radiation pattern setup of the four-element Phased Antenna Array System. Before starting the measurements, the protractor was used to adjust the elevation to \(42^{\circ}\). The ground plane of the antenna array was provided with a fixing system perfectly adapted to that of the antenna positioner for the safe fixing of the entire system that formed the array. At each measurement of the radiation pattern, the positioner, together with the antenna array fixed on it, performed a full rotation movement of 360\({}^{\circ}\) around the center of the discoidal ground plane of the array. The signals received by the antenna array were then amplified and processed by the data acquisition interface. Via the specialized software of the Lab-Volt equipment, the signals were processed and recorded to display the radiation patterns with a 1\({}^{\circ}\) resolution in the horizontal (azimuth) plane.