Qpsk Modem Design And Fpga Implementation

QPSK modulation has the virtue of high spectrum efficiency, fast transmission speed, strong anti-jamming and good spectrum. It's widely used in mobile communication and satellite communication. Therefore, the study of all-digital QPSK modulation and demodulation based on FPGA has important significance.Firstly, this dissertation introduces the present situation of QPSK modulation and demodulation technology, mainly a detailed description of the development and hardware platform of it. Then, it analysises the basic principle and composition of QPSK modulation and demodulation system, including the basic principle of RS coding and decoding, Convolution coding, Viterbi decoding, interweaves coding, DDC, Carrier synchronization and Bit synchronization. On that basis, simulations are taken to verify the performance of each module, and then the algorithm is converted to HDL description for FPGA realization. The resource consumption of modulation system and demodulation system is given respectively. Finally, it gives the introduction of the hardware platform of the system realization, the analysis of the system performance, and detailed description of DA chip's configuration on the modulation side.Meanwhile, the design of the modulator given in this paper has been successfully applied to the radar information transmission of QPSK digital modems in frequency, symbol rate 8MSPS, the frequent rate of 60MHz. And the design meets the technical requirements of the project. At the same time, the Phase unwrapping of the internal code fast estimation algorithm proposed can successfully replace the QDPSK in the differential encoding and decoding programs, which uses Viterbi soft-decision to improve the coding gain of the system.