Research And Implement Of PSK Modem In Spread Spectrum Communication Using FPGA

Nowadays, Software Radio(SR) has been becoming a hot research in the field of Wireless Communications, especially in the intermediate frequency(IF) digitization receive. The core thought of SR is making the high-speed broadband A/D and D/A near the antenna as close as possible and making inter-specific scheme of IF digitally, in order to implement more function of wireless by using software. Thesis places emphasis on the Digital Down Conversion(DDC) and the modem in a Wireless Spread Spectrum Communication system, based on Software radio. They are designed and completed in FPGA which used modern DSP technology.This paper places the related theories about numerical controlled oscillator(NCO) fristly. And then design a module of NCO using DSPbuilder in order to engender sine and cosine wave for DDC and modulator . Then, it researched CIC filter,FIR filter and HB filter in this paper, and implemented the module of DDC in DSPbuilder. Thesis confirm two modem project of DPSK and QPSK according to the channel environment and the different transmission speed's request, after researched many kinds of modem system. The DPSK modem used the differential coherent detection to complete data demodulation, while, the QPSK modem used quadrature coherent demodulation based on carrier synchronization. This paper choosed Costas to impletment carrier synchronization after analysis and simulation. After all, the modems is completed under the DSPbuilder software environment.After finished the software works, the Documents of ".mdl" should be switched in to ".hdl".,under the QuartusII 7.2 environment, these ".hdl" documents are compiled,simulated and downloaded to hardware platform, which is based on EP3C40Q240C8FPGA chip. The results prove that these schemes are correct.