High-speed FFT processors based on redundant number systems

Fast Fourier Transform (FFT) processors, having a significant impact on the performance of communication systems, have been a hot topic of research for many years. FFT function consists of consecutive multiply-add operations over complex numbers, dubbed as butterfly units. Use of redundant number systems is a way of increasing the speed of FFT coprocessors. It eliminates carry-propagation and hence permits latency reduction of each stage of the pipelined FFT architecture. This paper proposes a high-speed FFT processor using the devised fused-dot-product-add (FDPA) unit, to compute AB ± CD ± E, based on Binary-Signed-Digit (BSD) representation. Three-operand BSD adder and BSD constant multiplier are the constituents of the proposed FDPA unit. A carry-limited BSD adder is proposed and used in the three-operand adder and in the parallel BSD multiplier, so as to improve the speed of the FDPA unit. Moreover, modified-booth encoding is used to accelerate the BSD multiplier. Synthesis results show that the proposed design is about two times faster than the best previous work; but at cost of more area/power consumption.