MOBILE SATELLITE COMMUNICATION SYSTEM WITH PASSIVE TERMINALS BASED ON MODULATING RETRO-REFLECTORS

Abstract

In this work, a qualitative and quantitative comparison of satellite mobile communications systems with various altitudes of the orbits of spacecraft was carried out. A study of the conditions for the spacecraft to be located in the visibility range of the ground terminal and an analysis of the time spent by the satellite in the visibility zone depending on the height of the orbit was made. According to the results of this analysis and taking into account the fact that the low orbit area around the Earth is very densely filled with artificial satellites and space debris, it can be concluded that it is advisable to increase the radius of the orbit of telecommunication satellites. At the same time the geostationary orbit, which has obvious advantages in terms of coverage, is also quite densely filled with spacecraft, and is very high for the efficient operation of low-power mobile ground terminals. Taking into account these features, it is concluded that the use of medium-height orbits for telecommunication satellite systems is promising for which global coverage of the Earth’s surface can be achieved using several dozen satellites. In addition, the distance to the Earth’s surface will be small enough to provide a high signal-to-noise ratio and, as a result, the system will provide a high bitrate. A computer simulation of the operation of a satellite telecommunication system was carried out for a different number of spacecraft and various parameters of their orbits in order to determine the conditions for achieving global coverage. This simulation confirms the conclusions regarding the feasibility of using medium orbits. The concept of using passive terminals based on modulating retroreflectors was proposed. It means the reflection of a satellite signal by a ground terminal without emitting its own electromagnetic energy. The energy of the terminals is spent only on the modulation of the reflected signal. This approach will significantly reduce the energy consumption of ground terminals and thereby increase mobility. It is proposed to carry out phase and polarization modulation of the signal using liquid crystals or metamaterials.