Design And Simulation Of π / 4-DQPSK Modem Technology Based On

Large communication capability, far distance and high transmission quality are required in modern communication system. Modulation and demodulation, which is one of the most key techniques in communication, has always been an important aspect of researching field. In a certain extent, the quality of the demodulation algorithm determines the quality and efficiency of the communication system directly.This research paper is based FPGA modem technology; the paper realized the modulation and demodulation. The technology of p/4-DQPSK is a modified form of QPSK modulation is a modification, which is a narrow-band digital modulation technique, characterized by the spectral characteristics of good, strong anti-fading, high bandwidth efficiency.Firstly, we studied and analyzed the basic principles of modulation and demodulation. Our attention focused on the differential encoding technology and shaping filtering techniques in modulation system, we compares the roll-off factor for the performance indicators were0,0.5,1square root raised cosine filter in MATLAB simulation. In demodulation system compared the frequency differential demodulation, baseband differential demodulation techniques both demodulation method chosen baseband differential demodulation finally.Secondly, according to the p/4-DQPSK modem we encountered in achieving carrier synchronization, symbol synchronization problems, researched Costas loop algorithm, lead-lag door synchronization algorithm theory, analysis and simulate the theoretical of key modules loop filter module and sooner or later-the door data acquisition module.Finally, we used the hardware of FPGA description language Verilog HDL,designed and simulated each module in Altera’s QUARTUS Ⅱ development environment, at last we achieved the FPGA-based p/4-DQPSK modem and synchronization functions by compiling and comprehensing of modulation.