Low-Power Split-Radix FFT Processors Using Radix-2 Butterfly Units

Abstract

Split-radix fast Fourier transform (SRFFT) is an ideal candidate for the implementation of a low-power FFT processor, because it has the lowest number of arithmetic operations among all the FFT algorithms. In the design of such processors, an efficient addressing scheme for FFT data as well as twiddle factors is required. The signal flow graph of SRFFT is the same as radix-2 FFT, and therefore, the conventional address generation schemes of FFT data could also be applied to SRFFT. However, SRFFT has irregular locations of twiddle factors and forbids the application of radix-2 address generation methods. This brief presents a shared-memory low-power SRFFT processor architecture. We show that SRFFT can be computed by using a modified radix-2 butterfly unit. The butterfly unit exploits the multiplier-gating technique to save dynamic power at the expense of using more hardware resources. In addition, two novel address generation algorithms for both the trivial and nontrivial twiddle factors are developed. Simulation results show that compared with the conventional radix-2 shared-memory implementations, the proposed design achieves over 20% lower power consumption when computing a 1024-point complex-valued transform.