Design And Implementation Of Modulation And Demodulation System For Deep Space Communication

Deep space communication technology is the basis of deep space exploration activities, all the data transmission and remote sensing information of deep space exploration tasks should be passe d through the communication system. As a carrier of the deep space communication, the technology of modulation and demodulation is a key link in deep space communication system, so it is necessary to study the communication model used in deep space channel and the key technology of modulation and demodulation. This paper studied the technology of modulation and demodulation for deep space communication, and implemented a multiple modulation and demodulation system with the function of deep space channel simulation, so it's a good experiment platform for the study of deep space communication, and it is of great significance to the study of deep space communication.First, the paper introduces the research background and current situation of the deep space communication technology, and state the significance of the study on technology of modulation and demodulation for deep space communication. And took theoretical study and simulation about the technology of constant envelope modulation for deep space communication, and the characteristic and parameters of the the deep space channel are studied.Second, the structure and index of the modulation and demodulation system is designed in the way of software defined radio. The transmit and receive of data between the PC and hardware is inplemented in the way of EDMA data transmission controled by the DSP. Interpolation, up-conversion, down-conversion and the channel simulation is inplemented by the FPGA, and the coherent demodulation is inplemented in the method of costas loop.Then, the structure of the software part of the system is designed and implemented, the PCI driver program is writen to inplement the data communication between the PC and DSP. In the transmitter, BPSK, QPSK, OQPSK, FQPSK, GMSK, FM and PM in 12 different data rate are inplemented in the method of multistage interplation, the parameters of channel are designed to setted by software, and symbol synchronization is designed in the method of early-late gate baseband loop.Finally, tests of the system are conducted and the function and parameters of the system have been tested. The result shows that the modulation and demodulation system runs well and all the functions have been inplemented, and this system can satisfy the design indexes, so this is a good experiment and test platform for subsequent research on deep space communication system simulation.