Research On Separation Technologies For Co-Frequency Signals Of Satellite Spot-Beam

Around the key technologies of blind separation for co-frequency signals of satellite spot-beam,this paper focus on the mixed signal detection and the component signal number estimation,amplitude estimation,blind separation algorithm based on SIC for symmetric mixed signals and low complexity blind separation algorithm for non-symmetric mixed signals,etc.The main work and innovation are summarized as follows:1.Aimed at the problem of the mixed signal detection and the component signal number estimation for co-frequency signals of satellite spot-beam.This paper firstly proposes an algorithm for the mixed signal detection and the component signal number estimation based on spectral line feature.The algorithm realizes the function by calculating the M spectrum of the mixed signals,setting the threshold value and extracting the discrete spectral lines which expressed the frequency offset of the component signal.Simulation results show the effectiveness of the proposed algorithm.But the computational complexity of the algorithm is high,and when the mixed signal modulation order is higher or the frequency offset of the component is equal,the algorithm is invalid.In view of this,a new algorithm for estimating the number of components of the mixed signal based on the data aided is proposed.The algorithm realize the estimation of the number of the mixed signal components by the correlation operation between the received signal and the synchronous symbols,frame accumulation,setting the fixed threshold value,extracting the peak spectral line.The simulation results show that the algorithm has low complexity,and it has no relation with the mixed signal modulation order and the frequency offset of the component.The algorithm has a very good practical prospects.2.Aimed at the problem of amplitude estimation for co-frequency signals of satellite spot-beam.This paper proposes a low complexity amplitude estimation algorithm,using the maximum like-hood criterion.Based on deriving the like-hood function,the algorithm realize the amplitude estimation of component signals pass the condition of maximum like-hood function when signal frame size and synchronization head symbol are known.Meanwhile,the performance bound of signal-channel co-frequency mixed signals is derived to provide the theoretical basis of algorithm capability.Simulation results show that,the normalized mean square error of amplitude estimation can reach 10^-4 when signal frame size reaches 40 frames,coming close to performance bound.Moreover,the proposed algorithm applies to low-order and high-order single-channel co-frequency mixed signals.3.Aimed at the problem of symmetric mixed signal blind separation algorithm for co-frequency signals of satellite spot-beam.This paper study on a low complexity blind separation algorithm based on the serial interference cancellation algorithm,and applies it to the blind separation of the mixed signal of the co-frequency of 8PSK.The algorithm transforms the single channel model of mixed signal into multi-channel model through sampling,and modifies the influence of channel truncation in channel reconstruction which avoids the loss of separation performance.The simulation experiments show that the algorithm has similar performance with existing algorithms,but its complexity is reduced by two-thirds,and it is not sensitive to the frequency offset.In addition,the separation performance of 8PSK modulation method is two orders of magnitude lower than that of the QPSK modulation method.4.Aimed at the high complexity problem of non-symmetric mixed signal blind separation algorithm for co-frequency signals of satellite spot-beam.This paper proposes a low complexity blind separation algorithm for non-symmetric mixed signal blind separation.This algorithm firstly determines the best sampling time of strong signal,and then the interference of strong signal is removed,avoiding the waveform reconstruction process in traditional algorithm.The iterative decoding structure is used to improve the separation performance.With special emphasis on the remove of strong signal in asymmetric mixed signal and the iterative decoding structure of the asymmetric mixed signal.Simulation results show that,for QPSK signals with?2,1,2?convolutional codes,the best separation performance can be obtain when the amplitude ratio between strong signal and weak signal was 0.5,a gain of about 1dB separation performance can be obtain after two iterations.