a modular fast fourier transform processor which employs identical processor cards , each of which has a butterfly , memory units which send and receive data to and from the butterfly and a pair of input ports and a pair of output ports . the cards are interconnected through these ports to execute a fast fourier transform decomposition in accord with singleton &# 39 ; s algorithm . the speed and capacity of the processor may be increased in a gradual manner by employing more of the processor cards .