The Design And Implementation Of Digital Satellite TV QPSK/QAM Trans-Modulator

In the Digital Cable TV network, it is important process to translate the Digital Satellite TV (DVB-S) to Digital Cable TV (DVB-C). The structure and cost of the systems of Digital Cable TV Front-End vary with the solution of it. The existing solution uses the single function modules, which are full capacity in signal processing and complete independence in structure, to build the Digital Cable TV Front-End. When the building block modules are used for building the Front-End systems to pickup multi programs been send by MCPC way, the capacities of the modules are not full used. Furthermore, the Digital Satellite TV receivers in the solution tend to use the special de-multiplex/control chip, which is costly, but whose functions are not been full used in such receiver. All of those are disadvantage in cutting down the cost of front-end.In the paper, a solution of QPSK/QAM Trans-Modulation is presented for DVB-S to DVB-C. The QPSK/QAM Trans-Modulation offsets the shortcoming of the existing solution. The design implements all of the functions in a single box, which includes Digital Satellite TV Receiver, Program Filter, QAM Modulate, Digital Quadrature IF Modulate, and Adjacent Channel Modulator, also implements an ASI interface for extra MPEG2 Transport Stream input. This Trans-Modulator is delicately designed to been used in Translating multi-program been send by MCPC way. The presented architecture provides a high performance, low cost, flexible and efficient alternative solution, which briefs the Digital Cable TV Front-End and cuts down the cost of it, for Digital Cable TV Front-End.In the paper, the signal processing flows and the elementary theory of it is introduced. The main parts of the system are designed and implemented, such as: Single Zero IF Tuner, Program Filter based FPGA and DSP, QAM Modulator, Digital Quadrature IF Modulate, and Adjacent Channel Modulator. The protocol of communication of the Program Filter, The software flows of the Program, and the main software flows of the system are discussed.The first trial-produce, according to the scheme, is success. It has met the designed requirements. The experiment proves the design scheme is feasible. At the end of the paper, the successes in the development are summarized.