FPGA Implementation Of Spectrum Sensing Function Of Cognitive Radio

Key technologies and a hardware implementation of spectrum sensing used in Cognitive Radio (CR) System are presented in this paper. Firstly, the hardware implementation architecture of the spectrum sensing function of CR is proposed, including the RF front-end module and digital signal processing module. Secondly, all the components' functions and characteristics of the RF front-end module are shortly introduced. Finally, the hardware implementation and verification processes based on FPGA are presented in detail.Digital signal processing module aims to obtain the Short-Time Fourier Transform (STFT) of broad-band signals. It feeds a broadband intermediate-frequency signal to a digital down convertor which is based on a poly-phase filter bank. And then, data frames of each base-band channel are over lapped and windowed. At last, the time-and-spectrum relationship of the signal is displayed via Fast Fourier Transform (FFT) analysis. The whole system is composed of delay-decimation module, ploy-phase filter module, 32-point pipelining FFT module, sliding data buffers, 256-point pipelining FFT module and so forth.This design is built on Virtex-4 XC4VSX35 FPGA of the Xilnx Corp using hardware descriptive language called Verilog HDL. A synchronous method is adopted in the whole system, so that the system can run steadily under 200MHz clock. Its analysis spectrum bandwidth is up to 65MHz, which is proved of the high value in practical applications.