Serial Butterflies for Non-Power-of-Two FFT Architectures in 5G and Beyond

This paper presents new serial butterflies for non-power-of-two (NP2) fast Fourier transform (FFT) architectures. The paper considers radices 2, 3, 4, and 5, which are used in FFTs for 5G systems. Current designs for non-power-of-two FFTs are mostly based on the single-path delay feedback (SDF) architecture. This type of architecture processes data arriving in series. However, it uses butterflies with several parallel inputs. This results in low utilization, as the butterflies have to wait for all the inputs before they start to process them. Conversely, the proposed approach allows to calculate the butterflies on data that arrive in series. This removes waiting times and reduces the number of hardware components such as multipliers and adders. As a result, the proposed butterflies achieve high performance and provide a significant reduction in area and power consumption with respect to parallel butterflies. Thus, they are an efficient solution when data must be processed in series in the butterflies.