ASIC Design of Radix-2, 8-point FFT Processor

Abstract

In split radix architecture, large sizes Fast Fourier Transforms (FFT) are decomposed into small independent computations to reduce storage burden. Radix-2, 8 point is one the popular choice in split radix for small independent computation. Author proposes the FFT processor architecture for this small independent computation i.e. radix-2, 8-point FFT. This paper brief architecture comprising Butterfly Unit (BU), register set and controller. The novelty of this architecture is that it replaces the series of Processing Elements (PE) by single BU. BU computes two halves of the computations concurrently. Arithmetic computations are performed in floating point form to overcome the nonlinearities. All computations are controlled by tailored instruction set. All instructions are of same size and have same execution time. Twiddle constants are implicitly available in the instruction. Internal computations are stored in register set to avoid the load and store operations with memory. The mean square error of the computation is reduced by 41.95 % and 55.76 % in magnitude and phase respectively as compared with computations performed by rounding the twiddle constant. This FFT processor is synthesized, placed and routed for 45 nm technology of nangate open cell library. The BU of this architecture is 18 % smaller and 5 % faster as compared with smallest and fastest BU reported previously. The hardware cost metric i.e.    D_p mm² ns² mW = 1.37 of proposed processor and 32.51 % less as compared with the previous work.