FPGA Implementations Of Fast Fourier Transforms Algorithm

OFDM(orthogonal Frequency Division Multiplexing)have been researched,when the fast development of digital signal processing technical in communication field. It transfers by many carrier waves in wireless. OFDM have the advantage of the low rate of mistaking code and dissertation, the high transfer speed. OFDM will become the fourth generation mobile communication system in future. When the FFT algorithm replace DFT algorithm, it decreased the degree of complex of computation rapidly. Because of the development of VLIC (Very Large Integrated Circuit), the programmable logic controller such as FPGA is proposed. The programmable logic controller provides the hardware implement foundation of FFT processor. Thus we can implement FFT algorithm in the module of modulate and demodulate part in OFDM system. It is necessary to research FFT algorithm.In this essay, I study the mathematics theory of FFT algorithm, especially in the diagram of FFT algorithm data flow. I design one OFDM system after introduce the principle of OFDM system. Then I introduce the programmable logic controller, hardware description language and the emulation software, for they are the implement foundation of OFDM system. I choose DIF-FFT radix-2 algorithms to design FFT processor which can be used in the module of modulate and demodulate. The FFT processor is designed by VHDL. It translates and compiles, synthesizes, emulates by Quartus II software platform. The result shows that it is 108.5 microsecond to complete a 512 points butterfly computation, which satisfy the need of high speed transfer and process. I use the designed FFT processor as the module of modulate and demodulate. Then I use 75MHz as the clock frequency in the OFDM system. The emulation shows the system works well.