Antenna Array Optimization Of MIMO System Based On Cooperated Leo Satellite Formation

With the development of space technology in recent decades, the task of artificial satellite is more complex, cause more and more space data need to be transmitted, it is urgent to explore a new technology to fast transmit the satellite data to the ground. At the same time, with the increase of the number of satellites, the non-renewable synchronous track are crowded, so the use of nonsynchronous orbit is the hotspot of future satellite application. Low Earth orbit(LEO) satellite formation flying with each other, have the advantages that a single satellite can’t match, is the focus of research in the field of space application. The use of spatial resources of satellite formation can effectively improve the data transmission rate by Multiple Input Multiple Output(MIMO) technology in satellite communications. According to the Line of Sight(LOS) MIMO theory, the MIMO sub channel orthogonality can be achieved by using the specific parameters of the antenna array. While the LEO satellite is in high speed motion state, the parameters of a fixed antenna array can’t maintain the capacity of the MIMO system.In this paper, we mainly study the application of MIMO to the satellites communication system of low earth orbit formation flying satellites to ground station. Through the study of the satellite downlink to earth, we know because of the frequency of the satellite communications is high, so the beam is high pointed. Based on the existing formation satellites cooperative communication research and the MIMO theory, this paper proposes a transmission mechanism based on the LEO formation satellites cooperative communication, which applied LOS MIMO technology in formation flying satellites communication with ground array, and introduces the antenna array optimization method based on max MIMO capacity in the wireless fading channel. By the STK and Matlab software, the MIMO model of the satellite formation is established, and then simulate of the performance of the antenna array parameter optimization method. The simulation results show that the optimization of the antenna array parameters can maintain the orthogonality of the sub channels of the LOS MIMO system, so that the capacity of the LOS MIMO channel can be maximized in the communication time window of a low orbit satellite formation is visible to ground station. Finally a simulation analysis of the influence of ground antenna array optimal spacing error and the error of satellite position on the channel capacity of a system, shows that with using antenna array parameter optimization method, the application of LOS MIMO into formation flying satellites communication with ground formations not only can increase the channel capacity of the system, but also have certain error tolerance. It is proved that the proposed antenna array parameter optimization scheme base on LEO satellite formation MIMO system has certain engineering application value.