# The Design and Implementation of a Phased Antenna Array System for LEO Satellite Communications
## 4 Controlled Reception of LEO Satellites Using the Proposed Phased Antenna Array System  
Figure 4 shows a simplified schematic representation of the principle of controlled reception of a certain LEO satellite, using the potential of the proposed phased antenna array system for this specific application, further demonstrated in this article. In its current state, this system represents an innovative concept whose functionality has been demonstrated in this article and which is ready to be implemented in similar reception systems. To ensure clarity, we have delimited the proposed phased antenna array system with a dotted rectangular outline so as to distinguish it clearly from the other elements in the reception chain. The following segment will succinctly explain the operational mechanism of a reception system based on the simplified depiction in Figure 4.  
The signals received by each element of the array are phase-shifted in a controlled manner and then summed. The resulting RF signal is used by the ground station to receive information transmitted using LEO satellites. Certain values of the phase shifts of the elements correspond to a certain angle of main lobe orientation in the azimuthal plane. By changing the phase shifts, the computational system can almost instantly change that orientation angle. In Figure 4, the main lobe provided using the phased antenna array is illustrated. In the vertical plane, the array has the maximum gain in the medium elevation range, which is favorable for the LEO satellite reception, and in the azimuth plane, it is oriented towards one of the satellites. An analysis of the phased antenna array's radiation pattern in a vertical plane is provided in the next section. Orbitron [31] is one of the free satellite tracking systems for satellite communication users, weather professionals, astronomers, astrophysicists, and many other users. The azimuth angle values of the satellite provided using the Orbitron software in real-time can be input into the developed control software which further controls the module of the phased antenna array's main radiation lobe orientation angle. Based on the satellite azimuth (\(\varphi_{0}\)), which can be imported from the satellite tracking system; the values of the phase shifts (w1, w2, w3, w4) can be derived according to Equations (10)-(13) and then  
Figure 4: The principle of controlled reception of LEO satellites using the proposed Phased Antenna Array System. The four radiant elements of the phased antenna array system were noted from 1 to 4 (on the left side of the figure). applied to the signals received by the four elements. Thus, the main lobe of the antenna array can be oriented to this azimuth angle. In the figure shown above, the term Computational system refers to a more general computing system, such as SBC (Single Board Computer) type Raspberry Pi, STM32 MP1 (produced by STMicroelectronics, a multinational corporation with headquarters in Planles-Ouates, Switzerland ) can also be used. This system runs the satellite tracking software (that provides real-time azimuth angle values of the LEO satellites) and also runs the software for controlling the main lobe orientation of the phased antenna array system and integrates the azimuth angle values to track the LEO satellites. The computed values are provided to the phase shifters control module in binary format. Regarding the phased antenna array system itself, which is the main subject of this article, we will briefly present its component elements in Section 5. The Phase shifters control module is based on a Teensy 4.0 [32] development board that contains the ARM Cortex-M7 processor, which offers significantly higher operating speed compared to conventional 32-bit processors. Its primary function is to receive binary values provided by the computer via a USB connection and serially transmit them to the phase shifters, through which the phase shifts of the supply signals of the four elements of the phased antenna array are introduced.