The Research And Realization On Digital Modulation And Demodulation Based On Software Radio

In recent 20 years, the mobile communication develops rapidly .At present, it is in transition from the second generation to the third generation . The modulation and demodulation is a key technology in mobile, and it is important for mobile communication to select a appropriate and high effective modulation mode according to different wireless channel characteristic. The appearance of the software radio is a huge impetus to the development of mobile. Constructing a general,standard and modular hardware platform and realizing the radio function by software instead of hardware can enhance the system flexibility greatly. It is flexible for the modulation and demodulation by software, and it may realize different modulation mode through the airborne downloading ,therefore it suits the different communication systems.After reading massive domestic and foreign literature about modulation and software radio, the principle, merit and defect of each kind of digital modulation mode is studied in the paper , A software radio platform is designed. The platform takes TI's DSP chip TMS320VC5416 as the core,used to complete each kind of digital modulation and demodulation algorithm.Expanded AD and DA module on the periphery electric circuit, used to realize the conversion between the analog and the digital signal, and uses CPLD to realize the address allocation and to provide the interface control signal. Having realized the modulation and demodulation algorithm of ASK,FSK,QPSK on the software radio platform ,and has provided the modulation and demodulation flow chart and the main part procedure.This platform may not only realize each kind of digital modulation and demodulation, but also complete the function of baseband processing as a general experimental platform.