# The Design and Implementation of a Phased Antenna Array System for LEO Satellite Communications
## 5 Design and Implementation of the Phased Antenna Array System for Leo Satellite Communications
The high-performance Teensy 4.0 development module included an ARM Cortex-M7 at 600 MHz microcontroller with the possibility of overclocking up to 1 GHz, float point math unit--64 and 32 bits, 1984K Flash, 1024K RAM, USB device 480 Mbit/sec and USB host 480 Mbit/sec was used for controlling the phased antenna array's main radiation lobe orientation in the azimuth plane. As shown in Section 4, the data regarding the satellite azimuth angle can be imported from Orbitron software, the phase shift values (w1, w2, w3, w4) given by (10)-(13) and applied to the signals received by the four antenna array elements being dependent on that azimuth angle, \(\varphi_{0}\). The phase shifters control software was written using the C++ programming language, extended with the Teensy 4.0 specific add-on. Although the AD8340 circuit has the ability to adjust the signal amplitude as well, this facility has not been used, keeping the attenuation to a minimum to give the antenna array maximum sensitivity. Figure 11 can be seen as a simplified diagram of how the software works for programming a phase shifter. The programming of each of the four-phase shifters was based on the same software diagram. The phase shifters were previously tested within linear antenna arrays in the 868 MHz and 915 MHz frequency bands [38; 39]. The frequency range for the AD8340 vector modulator circuit is 700 MHz-1 GHz. Given the availability of these phase shifters, in the idea of using them for a lower frequency range assigned to the reception of LEO satellites, many preliminary operation tests of those were carried out in the 435 MHz band. Figure 12 shows the results obtained from these laboratory tests. The phase shifts introduced by the four-phase shifters (PS1-PS4) implemented in the phased antenna array had very close values for the same phase setpoints. The graph of Phase shifts vs. Phase setpoints indicates an acceptable correspondence between the phases achieved by the PSs and the phase setpoints, being close to the graphs for (700 MHz-1 GHz) in the AD8340 datasheet. The module can be seen in Figure 13. The \"Minicircuits\" splitter/combiner shows linear characteristics in a very wide frequency band, including the one of interest to us, located between 435 MHz and 438 MHz [35]. Figure 11: The logical diagram of phase shifters control software. In order to make the signal processing part more compact, a module containing the phase shifters, the phase shifters control module, the splitter/combiner, and the USB programming interface were developed. In designing and making the PCB needed for this module, the distance between the component elements and the need to make an electromagnetic shield for the phase shifters were taken into account. To minimize signal attenuation and introduce additional phase shifts, SM-SM50+ adapter connectors were used to connect the four outputs of the phase shifter to the inputs of the combiner. The power supply system was initially thought to provide autonomy in the process of measuring the radiation pattern of the antenna array so that there was no need for extra power wires that could disturb the rotation movement of the Lab-Volt antenna positioner during the radiation pattern measurements. The battery-based power supply uses LiFePO4 technology, which requires no maintenance, allows for quick charging, and is environmentally friendly.