Design And Realization Of Multibeam Communication Device Based On Air-ground Communication

With the development of various aircrafts in the Earth-nearing space, the demand for wideband air-ground communications is growing rapidly. It is a significant research issue to establish a reliable and flexible data transmission link in the space to make the blast-off platform to be able to suit various communication tasks.As a special communication system, the air-ground communication system is usually used for regional communication. Since the blast-off platform is always in moving status, the antennas of the platform and any Earth terminal station must be aligned with each other by means of antenna servo devices for keeping the air-ground link, in which the technique requirement of the antenna servo tracking is rather high. In the existing system of ground to air communications, the ground station usually adopts directional antenna with high gain, while the blast-off platform can use either omni or directional antenna, in which there exists great difficulty not only in further raising bandwidth utilizing rate, but also in further improving the performance of the user links in a wide coverage area.After analyzing the characteristics of air-ground communications and the previously stated limitations of the conventional air-ground microwave communication systems based on the antenna servo, this thesis proposes a new scheme for such communication systems basing on multi-beam technique, moreover the author along with his colleagues have it implemented. The related research work is presented as follows.Firstly, the thesis introduces the research background and the significance as well as the present situation of the domestic and abroad on the related research area, involving some brief description about the principle and history of the air-ground communication as well as its advantages compared with other wireless communications. Then we give the design ideas and implementation method to construct an air-ground communication system, including a detailed analysis of the composition and working principle of the system. Through analyzing the specification limitations of the existing air-ground communications, we give the design and realization method of a multi-beam antenna communication system which is able to overcome the drawbacks, mainly using multi-beam smart antenna and ad hoc network techniques. Some theoretic analysis, design idea of hardware and software and key techniques about the system are also presented. Finally, the thesis provides some experimental test data. The test results show that the developed system has reached the expect goal, and has some useful characteristics. For example, its user capacity can be remarkably increased compared with the conventional air-ground communication systems, because it can support space division multiple access combined with TDMA or Ad hoc networking; it can quickly find and update the network neighbor nodes by beam scanning, to realize point to multipoint communication at the same time, so that it can form a network of supporting user’s freely moving; it can greatly improve the performance of user links, which benefits not only to making the user terminals compact but also to enhancing its anti-interference ability. In summary of the research work, the thesis indicates the way for further improving the system in the next phase of the project.