High-speed and low-power split-radix FFT

This paper presents a novel split-radix fast Fourier transform (SRFFT) pipeline architecture design. A mapping methodology has been developed to obtain regular and modular pipeline for split-radix algorithm. The pipeline is repartitioned to balance the latency between complex multiplication and butterfly operation by using carry-save addition. The number of complex multiplier is minimized via a bit-inverse and bit-reverse data scheduling scheme. One can also apply the design methodology described here to obtain regular and modular pipeline for the other Cooley-Tukey-based algorithms. For an N(= 2ⁿ)-point FFT, the requirements are log₄ N - 1 multipliers, 4log₄ N complex adders, and memory of size N - 1 complex words for data reordering. The initial latency is N + 2 · log₂ N clock cycles. On the average, it completes an N-point FFT in N clock cycles. From post-layout simulations, the maximum clock rate is 150 MHz (75 MHz) at 3.3 V (2.7 V), 25°C (100°C) using a 0.35-μm cell library from Avant!. A 64-point SRFFT pipeline design has been implemented and consumes 507 mW at 100 MHz, 3.3 v, and 25°C. Compared with a radix-2² FFT implementation, the power consumption is reduced by an amount of 15%, whereas the speed is improved by 14.5%.