Research And Implementation Of DQPSK Modulation And Demodulation Algorithm Based On Software Radio

Software radio technology is a new technology that has been developed along with mobile communication and microelectronics in recent years.Its main idea is to build a flexible,open and modular hardware platform on which software is used to implement the function of each module in various digital communication systems.As a guiding ideology and development direction,software radio is used a lot in the field of mobile communications nowadays.FPGA is one of the fastest developing software radio technologies.Digital modulation and demodulation technology plays a vital role in high-speed data communication,and DQPSK is widely used in modern communication systems due to its high frequency band utilization and strong anti-interference ability.Therefore,it is important to implement DQPSK modulation and demodulation with FPGA.This topic has carried out a comprehensive research on DQPSK modulation and demodulation algorithm in FPGA implementation,realized DQPSK full digital modulation and demodulation,the input signal code rate is 1Mbps,the modulator and demodulator design have reached the expected requirements.The paper first introduces the development and research status of software radio and digital modulation and demodulation technology,and analyzes the application prospect of FPGA in digital frequency band communication.In-depth study of the relevant theory of DQPSK modulation and demodulation provides a solid theoretical basis for specific circuit design.The modulation part is composed of a module such as a code converter,a shaping filter,an NCO and a multiplier,and the demodulation part is composed of a module such as a polar Costas loop,a bit synchronization loop,and a code converter.This paper focuses on the in-depth principle analysis of differential codec,polar Costas loop and bit synchronization loop,and introduces the FPGA design and simulation process and results of each module in detail.Based on the correctness of MATLAB modeling and verification design,using the Quartus II platform of Altera Corporation,the function design of each module in DQPSK modulation and demodulation algorithm is realized by Verilog HDL language.The function simulation is performed by ModelSim,and the simulation waveform is analyzed to verify the correctness of the algorithm.The tracking strategy of the polar Costas loop is further adjusted to reduce the frequency jitter after loop convergence and improve the demodulation performance.Finally,the channel check function is integrated in the DQPSK modulation and demodulation algorithm to improve the transmission performance of the system.The FPGA design and implementation of Hamming coding code are also carried out.