AN EFFICIENT FFT TWIDDLE FACTOR GENERATOR (ThuAmPO4)

Author(s) : Jen-Chuan Chih (National Chiao Tung University, Taiwan) Sau-Gee Chen (National Chiao Tung University, Taiwan)

Abstract : Twiddle factor (TF) generator is a key component in IFFT/FFT computation for current OFDM-based wireless and wireline communication systems, such as IEEE 802.11a/g, 802.16, VDSL, DVB, DAB systems. In this pa-per, we propose an efficient TF generator design. The pro-posed design combines an efficient conventional recursive sine/cosine function generation algorithm with a small compensation lookup table. The compensation table solves the error propagation problem of a recursive TF generator. It also costs less area than the existing modified recursive sine/cosine function generator. The proposed design requires only two constant multipliers, two adders, and two correc-tion tables, which is smaller than those polynomial-based complex sine function generators. Simulation results show that the proposed design is favourable over the existing TF generators for general FFT lengths in practical applications, except for small lengths such as 64 up to 512. For those s-mall FFT lengths, ROM-based is a better choice.

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