Fpga Based On Qpsk Modulation, Spread Spectrum Systems

QPSK is a linear narrowband modulation, which has the features of highspectrum utilization, better spectrum specification, stronger ability ofanti-fading and applicability of non-coherent detection. Spread SpectrumCommunication is a high performance technology developed with theapplication of military communication. It owns advantages of strongeranti-fading ability, better ability of combating the effect of multipathfading and higher security. It is widely used in the mobile communicationand satellite communication systems. Thus, it is significant to implementQPSK modulation in the spread spectrum communication system.Based on QPSK modulation in FPGA ,the direct sequence spread spectrumcommunication system is realized in this dissertation ,which has beencarried out in the following aspects: Firstly, the principle and thedevelopment of spread spectrum communication and QPSK modulation isintroduced ;Secondly, the following modules of the system had been completed,which included parallel-to-serial, serial-to-parallel, differentialencoding and decoding, DDS, spreading and dispreading,QPSK modulation anddemodulation. Verilog HDL language has been adopted for design andimplementing every module on the platform of QuartusII 4.1 of the AlteraCompany. The results of the simulation show that it works well.The spread spectrum system was designed with high integration and canbe upgradeable in software, which could provide for further designs withhigher integration and greater flexibility in the modern communicationsystem in the future.