The Research Into The High-Performance FFT Processor And The Accomplishment Of FPGA

At present, OFDM has become one of the basic implementation techniques in the future broadband wireless access systems as well as one of the first schemes to solve transmission problems of high-speed data in wireless channel. FFT/IFFT processor is the core data processing unit and is the key to realize data quadrature modulation and demodulation in OFDM system. The design of FFT/IFFT processor directly determines the performance of the OFDM system. In this paper, P2P handheld mobile device wireless communication baseband project was combined to design an OFDM system based point size variable high performance FFT/IFFT processor, which is compatible with 802.11g protocol.At first, the fundamental principle of OFDM system and its DFT implementation are introduced, and FFT basic designing theory is detailed analyzed. After comparing the amount of computation and complexity of all kinds of algorithms, combining with hardware implemented structure and configurable unit, the improved Radix-4 butterfly algorithm is adopted to design the processor. Four-channel paralleled data transmission is used, and Four-grade pipelining is adopted inside the butterfly unit, by which the processing speed of the system is improved. According to the characteristics of data flow baseband project, both input and output are processed by using ping-pong ram which effectively finishes the continuous data flow processing. Through analyzing operational rules of system required three different points, 64 points, 256 points, and 1024 points, the points variable configuration scheme was designed. By controlling selection of each butterfly operation and reusing butterfly unit, the hardware overhead is greatly reduced. Different points conflict-free addressing scheme is proposed, and Four-channel paralleled data simultaneous operation is achieved, and meanwhile, the system errors and overflow are analyzed. Taking XILINX's XC5VFX70T of VIRTEX-5 series as the hardware platform, using ModeSim, ISE9.2, DC, Matlab and etc. as the software platform, and integrated test for this design was undertaken, the result shows that the highest working frequency of FFT after synthesizing is up to 166 MHz, under process of SMIC 0.18, the FFT processor after synthesizing is about to 0.54 mm2. Through a large number of joint tests for practical signal and data in P2P wireless communication project, the validity and practicability of the design are proved.