Based on the study of existing digital TV satellite broadcasting standards and a lot of relative papers, according to DVB-S (ETS 300 421) standard,considering DVB-S modulator algorithm, speed, resources, power consumption and other factors, an QPSK RF modulation program is proposed -AD9739 programs, the digital upcoversion modulation in which is achieved without a special chip. This design determines the required FPGA, and focusely solves the variable symbol rate in DVB-S modulator.
USB DVB-S Satellite TV Tuner Box - SatBox
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details include:channel coding, constellation maps, RF modulation (baseband shaping, half-band interpolation, CIC interpolation, polyphase filters, multi-phase digital frequency synthesizer, OSERDES module), AD9739 configuration module and ADF4350 configuration module.The system clock is produced by ADCLK914 combined with ADF4350, reducing the clock jitter to provide a stable clock for the system. The ADF4350 external filter is designed using ADIsimPLL software, to ensure the clock stability.In order to reduce the design difficulty and coding complexity, the randomization and convolutional interleaving modules use a new implementation approach.
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Convolutional coding uses a dynamic reconfigurable DCM for the realization of different rate modulation.For the verfication of the design and module code, this paper adopted Modelsim simulation, ChipScope and Matlab verification, ensuring the code accuracy. The AD9739 RF modulation is debugged in board level. This design makes full use of ChipScope debugging software of Xilinx corporation, verifies the system correctness by crawlling data and analysising its spectral.The system is realized on the XtremeDSP development board 4VSX35,and the modulation output performance indicators are tested using TV ExplorerⅡ+devices.