Multi-antenna Signals Combining Algorithm Based On Cooperated Formation Satellites

With the increasing of deep space exploration mission, the requirement for communication performance of deep space is also getting higher and higher. For the complex communication environment of deep space, we draw lessons from the concept of antenna arrays to build antenna arrays in space and synthetize the multi antenna signals. In this way the SNR can be effectively improved.Because of the relative movement between the formation flying satellites and ground receiving antenna, the signal delay difference and the frequency difference are nonlinear and time-varying which lead to the phase difference. This brings new problems to the parameters estimation for signal difference of synthesis technology. This article focus on the research of relative motion of formation satellites and the ground receiving antennas and use the signal synthesis technology to analyze the estimation and compensation problem of the time-varying frequency difference and phase difference. This paper focuses on the relative motion of two GEO formation satellites. According to the geometric relationship between the satellites and ground station and Hill equation of relative motion we give the time-varying expression of the delay difference and the frequency difference for the two signals. Then the compensation error is analyzed. Due to the compensation error, the influence on the signal-to-noise ratio of the synthetic signal from remaining time difference and frequency difference are also discussed. We join the delay difference and the frequency difference factor to obtain the expressions of antenna array synthesis signal-to-noise ratio.Theoretical analysis and simulation results show that the residual time delay and frequency difference cause the change of the phase difference, what’s more, the residual frequency difference makes the phase difference estimation performance and the synthesis SNR worse. At the same time, because of the residual frequency difference, the longer integral length for correlation algorithm doesn’t mean better synthetic performance, but makes the synthetic performance going down rapidly after more than a certain value range. Due to the effect of delay difference and frequency difference, the synthesis SNR has some loss. But we can still achieve ideal SNR gain. Therefore, the space antenna array cooperative reception model to improve SNR has certain reference function to the deep space communication.