Research On Key Technologies Of Blind Separation Of Satellite Signals In Single-Carrier Systems

Satellite communications are widely used in global communications.Due to the openness of satellite broadcast channels,the desired signal received by the group station will be interfered by third-party satellites in the same frequency,to reduce the quality of the desired signal reception,and in severe cases,it will cause satellite-ground communication interruption.This paper studies the key technologies of blind separation of satellite signals in the single-carrier system.First,the interference signal is identified by modulation recognition,communication parameters estimation,time-frequency synchronization,and then the reconstruction and cancellation of the interference signal are completed,targeted to isolate the desired signal.The specific research contents include the following three aspects.First,aiming at the problem of blind detection of satellite interference signals in the single-carrier system,the modulation recognition and communication parameters estimation algorithms are designed and verified.For the four modulation modes of BPSK,QPSK,8PSK and 16QAM,a modulation recognition algorithm based on decision tree is designed.Simulation shows that when the signal-to-noise ratio is greater than or equal to 8d B,the recognition rate is higher than 99%.The spectral refinement algorithm is used to estimate the symbol rate of the single-carrier satellite signal.When the signal-to-noise ratio is greater than or equal to 4d B,the normalized root mean square error is lower than10^-5.An improved roll-off factor estimation algorithm is proposed.Simulation shows that when the signal-to-noise ratio is greater than or equal to 5d B,the root mean square error is lower than 0.01.Second,aiming at the synchronization of the single-carrier system satellite interference signal,a symbol timing synchronization algorithm based on Gardner loop and a frequency synchronization algorithm based on phase-locked loop are designed and verified.The three-time interpolation Gardner loop time synchronization algorithm and the non-data-aided phase-locked loop frequency synchronization algorithm are respectively applied to the time-frequency correction of single-carrier satellite interference signals.The simulation results show that when the signal-to-noise ratio is8d B,the interference signal constellation after time synchronization and frequency synchronization can be corrected to the correct state,and the RMS EVM of the synchronized BPSK,QPSK,8PSK and 16QAM signal constellations are less than 5%.Third,aiming at the reconstruction and suppression of the single-carrier system satellite interference signal,the influence of the timing error on the interference signal suppression effect is theoretically analyzed..By infinite series expansion of the interference signal,an exact analytical expression of the jamming-cancellation ratio is derived.Moreover,we analyze the impact of the normalized time error and the roll-off factor on jamming-cancellation ratio.Simulation results show that the normalized time error of 0.1 causes a loss of 42d B in jamming-cancellation ratio,with the ideal received jamming-to-noise ratio of 60d B and the roll-off factor of 0.5.The research results of the thesis provide theoretical and method support for the blind separation of single-carrier satellite signals,which can be applied to the detection of single-carrier satellite signals.