Nigel C Morgan, 5156 Kristin Ct, Smyrna, DE 19977

4748579, May 31, 1988

Aug 14, 1985

6/765918

Israel B. Zibman - Newton MA
Nigel P. Morgan - Belmont MA

GTE Laboratories Incorporated - Waltham MA

G06F 15332

364726

A fast Fourier transform is performed under control of stretched out microcode. Sequential data inputs are multiplied by coefficients addressed by microcode in a digital multiplier. The resultant products are sequentially stored in three registers. The product stored in the second register is applied as one input to an arithmetic logic unit and the product stored in either the first or the third register is applied as the second input to the logic unit in order to compute the operation pairs (ax. +-. by). The Fourier transform is based on Winograd Fourier transforms modified for only real inputs and to force operations into the form (ax. +-. by). Sample points are initially scaled using the same circuit by performing an OR operation with respect to each sample point and an accumulated OR taken from the output of the ALU. The position of the most significant one bit in the final accumulated OR is indicative of the required scale factor. That scale factor is applied to the multiplier to scale each sample point.