Redundant and Online CORDIC for Unitary Transformations

Date
1994-08-20
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Abstract

Two-sided unitary transformations of arbitrary 2 x 2 matrices are needed in parallel algorithms based on Jacobi-like methods for eigenvalue and singulare value decompositions of complex matrices. This paper presents a two-sided unitary transformation structured to facilitate the integrated evaluation of parameters and application of the typically required tranformations using only the primitives afforded by CORDIC; thus enabling significant speedup in the computation of these transformations on special-purpose processor array architectures implementing Jacobi-like algorithms. We discuss implementation in (nonredundant) CORDIC to motivate and lead up to implementation in the redundant and on-line enhancements to CORDIC. Both variable and constant scale factor redundant (CFR) CORDIC approaches are detailed and it is shown that the transformations may be computed in 10n+o time, where n is the data precision in bits and o is a constant accounting for accumulated on-line delays. A more area-intesive approach uisng a novel on-line CORDIC encode angle summation/difference scheme reduces computation time to 6n+o. The area/time complexities involved in the various approaches are detailed.

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Keywords
CORDC, redudant arithmetic, online, unitary transformations, VLSI
Citation

N. D. Hemkumar and J. R. Cavallaro, "Redundant and Online CORDIC for Unitary Transformations," IEEE Transactions on Computers, vol. 43, no. 8, 1994.

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