The FPGA Implementation Of DPSK Demodulation System

In digital communication system, modem technology is a key technology. Modulation is simpler compared with demodulation. Whether the data can be received correctly or not lies in demodulation technology. Now digital technology has gained wide popularity,which further accelerates the development and application of demodulation technology.The development of software radio is growing quickly, coupled with the advancement of FPGA technology, the realization of a specific function integrated into a single chip shows great potential and will replace the traditional system design method, which becomes the new trend. Based on this method, the paper introduces a method to realize the full digital DPSK demodulation system using FPGA.Demodulation technology is of vital importance to receiving and sending the digital communications data and the quality of the phase-locked loop design is a decisive factor of the performance of demodulation system. Firstly, this article will elaborates the overall framework of the demodulation circuit.And then the detailed working principle, dynamic equations of carrier synchronization loop and the corresponding technical indicators are introduced. In view of the design, some important parameters are introduced in detail.What follows is the transition from the analog synchronous loop to the digital domain,which realizes the digital carrier synchronization loop and determines a various of parameters in detail. The design of digital carrier synchronization loop is a difficult keypoint. Its performance directly affects the result whether it can get the correct output or not. The modeling of the input signal is also critical. In this paper, a detailed introduction is also given about the input signal. Using MATLAB to generate engineering test data and performing early stage simulation of the whole system greatly save the design time.Lastly, the realization of the dfferential bit synchronization and the code type transformation are discussed and the whole simulation is done. On the whole, the input data of DPSK system is correctly demodulated.