Research On MF-TDMA/CWTDM Satellite Communications System

Continuous Wave Time Division Multiplex (CWTDM) is a technique of Non-regenerative On-board Baseband Processing (OBP) through which multiple continuous signals can be transmitted in a continuous channel by means of time division multiplexing. There are two methods to realize CWTDM, i.e. sub-frame overlap-adding method and sample-interweave method. However, both of them have insufficiencies. An improved sub-frame alternation method based on PN code is proposed in this thesis. Based on this CWTDM transmitting method, some researches on MF-TDMA/CWTDM satellite communications system proceed in this thesis, such as system design and link simulation. And performance analysis under AWGN is accomplished. What is more, the FPGA design of OBP of the system is implemented. Comparing with other systems, the advantages of MF-TDMA/CWTDM system are self-evident in system performance and on-board equipment complexity. The author's main contributions are as follows:1. An improved sub-frame alternation method based on PN code is proposed. The structure design of its transmitter, receiver and related modules, the simulations via MATLAB are completed, and the PN code and frame structure are designed.2. Using sub-frame alternation method based on PN code, some researches on MF-TDMA/CWTDM system are completed, including system scheme design, key techniques and system link analysis. The thesis also discusses the calculation of the power of noise, and has completed the simulations of the system link of transparent repeater scheme and MF-TDMA/CWTDM scheme via MATLAB, and researches the influence of accumulation of noise by comparing different systems.3. FPGA design of OBP of MF-TDMA/CWTDM system, including frame synchronization module, division and storage module and combination module are implemented. The basic functions of the modules have been validated by the simulation results. At last, the equipment complexity of this scheme is compared with that of regenerative scheme.