On preliminary design of bandwidth-on-demand high throughput satellite communications system technology

The R&D project entitled "Research and Development of Bandwidth-on-Demand High Throughput Satellite Communications System" has been started since 2016. The goal of the R&D is the realization of flexibility in frequency bandwidth for High Throughput Satellite (HTS) as well as the improvement of spectrum efficiency compared with current HTS. To realize the goal, the important technological challenges are to establish the wideband digital channelizer technology and the technology for miniaturization and integration of the feeder unit. Developed channelizer and multi-beam feeder technologies are planned be tested in orbit by the Engineering Test Satellite-9 (launch planned in 2021). Currently, we have been conducting the preliminary design of the system. At first, the system architecture of the satellite communications system was finalized, considering the progress of the system design. The mission requirement was broken down into the sub-system requirement related to this R&D (e.g. bandwidth/port, number of multi beam, target transmission speed) to verify the compliance. The analytical study of the payload employing flexibility in frequency bandwidth was also conducted. Following the basic theoretical model developed in the preliminary design, the model was enhanced to enable the evaluation with the temporal change of the traffic demand. The payload configuration, function, and performance requirement for the digital channelizer and multi-beam feeder was studied based on the system requirement study. Shared circuit with other subsystem and interface between the satellite bus were designed to finalize the preliminary design of the payload. Regarding the control methodology study for the payload employing flexibility in frequency bandwidth, control algorithms were installed to the simulator to verify the basic performance of the control system. Especially, the initial evaluation of the proposed "flexible channel allocation" method was performed to verify the effectiveness of the method. The items and equipment system of the performance test of the payload was studied to prepare the performance test planned in the final year of the R&D (2019). In the wideband digital channelizer technology, we evaluated the proposed signal processing algorithm to decrease the power consumption by using the partial breadboard model. We also designed the engineering model of the channelizer onboard the satellite with the ASIC design. In the feeder unit technology, the Single Feed Per Beam (SFPB) architecture, designed by the conceptual design of the multi-beam feeder, was evaluated by the partial model of the feeder antenna. Additionally, preliminary design was performed for the engineering model of the whole multi-beam antenna including reflector antenna. As described above, the preliminary design of the system was completed as the planned schedule.