An expandable column fft architecture using circuit switching networks

The Fast Fourier Transform (FFT) is widely used in various digital signal processing applications. The performance requirements for FFT in modern real-time applications has increased dramatically due to the high demand on capacity and performance of modern telecommunication systems, where FFT plays a major role. Software implementations of FFT running on a general purpose computer can no longer meet current speed requirements. However, recent advances in VLSI technology have made it possible to implement the entire FFT system on a single silicon substrate. This article presents a column FFT design suitable for ULSI (Ultra Large Scale Integration) implementations. The basic building block is a 64-point column FFT. FFTs with longer transform lengths can be easily realized using the 64-point column FFT building block. The butterfly processors in the column FFT are connected using circuit switching networks. The circuit switching networks not only provide dynamically recon-figurable interconnections among the butterfly processors, but also provide a fault-tolerant capability. Bit-serial arithmetic is used in the architecture. Assuming the data word length is 16 bits, the 1024-point column FFT engine proposed in this article is capable of processing 1024 complex data samples in 533 clock cycles. If the clock frequency is 40 MHz, it will take 13.3 µs to complete a 1024-point FFT.