Design And Implementation Of Signal Processing Modules In Phased Array Satellite Tracking Systems

Due to the advantages of fast scanning speed, flexible beam control and high anti-interference ability, satellite communication systems based on phased array antenna has been paid more universal attention. In modern satellite communication systems, array antennas are usually installed on moving carriers such as vehicles, ships and aircrafts. The motion of these carriers will lead to deviation of the beam direction from the satellite, which may cause communication failure. Therefore, how to track the satellite automatically and stably is a key issue. At present, automatic tracking technology for maneuvering targets is widely used in radar fields, but essays and research achievements about the satellite automatic tracking systems are relatively rare.Aiming at the realization of the phased array satellite tracking system in practical engineering, the principles of beam-forming, angle estimation and tracking filtering technology are analyzed in this dissertation. Then the performance of some common angle estimation methods and tracking filtering technologies are compared, and finally the implementation of the phase-comparison angle measurement algorithm based on FPGA is discussed in details.First, in this thesis the composition and the principles of phased array are presented. The overall framework of the system is designed and the basic theories and procedures of the main signal processing module are discribed, which lay the foundation for the later research.Second, the theory of beam-forming for the uniform planar array is introduced in this dissertation. Then performance comparison of the amplitude-comparison and phase-comparison angle measurement method is completed through simulation. Simulation results show that the precision of the phase-comparison angle measurement method is higher. So it is more proper to use the phase-comparison method for the satellite’s direction estimation in this system.Third, in this essay another key issue in the satellite tracking system-tracking filtering technology is also studied. The principles of three common tracking filtering algorithms are presentd, and after performance comparison, α-β filter is chosen as the tracking filtering strategy. Besides, the affection on the tracking performance caused by some imperfect factors, such as SNR, amplitude and phase error, beam pointing error and the carrier attitude measurement error is shown through simulation, which provides a theoretical reference for the realization of the tracking filter algorithm in actual engineering.Finally, details of how to implement the phase-comparison angle measurement algorithm in FPGA are described in this thesis, which mainly include the Verilog designs and simulation results of the preprocessing module, the basic calculation units using CORDIC algorithm, the calculation of phase-difference and angle calculation. The experimental results of the phase-comparison algorithm based on FPGA are presentd in this essay. The results show that the FPGA module in this dissertation correctly realizes the function of angle estimation. The azimuth measurement error is within 1.5 degrees and the elevation measurement error is within 1 degree.