A pipeline architecture for modified higher radix FFT

A method, called twiddle-factor-shift, which combines the simplicity of interconnections and processor elements (PEs) of radix-2 fast Fourier transform (FFT) algorithms and of the lower arithmetic complexity of higher radix FFTs is presented. The method is based on the linearity of the basic radix-2 operation and the data dependencies of the FFT. Twiddle-factor-shift means the cumulation or rotations of the complex samples every second or third stage of the FFT. This method offers an additional flexibility in the design of pipelined FFT architectures and leads to efficient PE and interconnection structures. An example of a modified radix-8 FFT architecture for a transformation length of N=256 that processes four samples in parallel and uses temporal permutation networks, which are optimal in the sense latency is given