Design of an efficient variable-length FFT processor

In this paper, we propose an efficient variable-length FFT processor architecture suitable for multi-mode and multi-standard OFDM communication systems. The FFT processor is based on radix-2² DIF FFT algorithm and also supports non-power-of-4 FFT computation. The design contains an efficient processing element (PE), which can execute radix-2² butterfly (BF) operations, as well as radix-2 BF operations. Moreover, in order to achieve high-performance variable-length FFT operations and data accesses, an efficient variable-length address generator and twiddle factor generator are designed. The design has the merits of low complexity and high speed performance. The designs consider seven different FFT lengths including 64, 256, 512, 1024, 2048, 4096, and 8192 points, which cover all the required FFT lengths by 802.11a, 802.16a, DAB, DVB-T, VDSL and ADSL.