Design And Implementation Of The Earth Terminal In The FDMA/CWTDM Satellite Communication System

One new satellite communication system based on onboard FDMA-CWTDM conversion could find wide applications, since it can overcome the two fatal drawbacks of FDMA/TDM system—too high the complexity of onboard processing equipment and less applicable the flexibility of the channels. In the process of developing the new satellite communication system, the design and implementation of the earth terminal is absolutely necessary to verify the onboard FDMA-CWTDM conversion and analyze performance of the system. Basing on the analysis of system architecture, principle and signal characteristics of the FDMA/CWTDM satellite communication system, this thesis puts emphases on the key techniques of the earth terminal transmitter and receiver. Main contributions of this thesis are as follows:1. Based on analyzing the key techniques and comparing various methods about the earth terminal transmitter, the model of the channelized transmitter is worked out using the software radio technique. The FDMA frequency hopping and spread spectrum signal earth terminal transmitter based on FPGA is implemented.2. Some practical algorithms for earth terminal receiver are proposed, and frame synchronization, CWTDM de-multiplexing, Time-hopping acquisition and de-hopping, DS acquisition circuits based on FPGA are implemented. A new kind of clock tracking loop based on FPGA is adopted to overcome the asynchrony of clock between the earth terminal and the onboard converter radically. Also, A robust method is adopted to implement some practical algorithms such as synchronization and decision, which ensures the stability and reliability of the earth terminal.3. The digital circuit design of the earth terminal is implemented. The software and hardware debugging, joint debugging and performance testing of the whole FDMA/CWTDM system are completed.