Radix-4 Vectoring CORDIC Algorithm and Architectures

  • Authors:
  • J. Villalba;E. L. Zapata;E. Antelo;J. D. Bruguera

  • Affiliations:
  • Dept. of Computer Architecture, University of Málaga, Málaga, Spain;Dept. of Computer Architecture, University of Málaga, Málaga, Spain;Dept. Electrónica, y Computación, University of Santiago de Compostela, Spain;Dept. Electrónica, y Computación, University of Santiago de Compostela, Spain

  • Venue:
  • Journal of VLSI Signal Processing Systems - Special issue on application specific systems, architectures and processors
  • Year:
  • 1998

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Abstract

In this work we extend the radix-4 CORDIC algorithm to the vectoringmode (the radix-4 CORDIC algorithm was proposed recently by the authors forthe rotation mode). The extension to the vectoring mode is notstraightforward, since the digit selection function is more complex in thevectoring case than in the rotation case; as in the rotation mode, the scalefactor is not constant. Although the radix-4 CORDIC algorithm in vectoringmode has a similar recurrence as the radix-4 division algorithm, there arespecific issues concerning the vectoring algorithm that demand dedicatedstudy. We present the digit selection for nonredundant and redundantarithmetic (following two different approaches: arithmetic comparisons andtable look-up), the computation and compensation of the scale factor, andthe implementation of the algorithm (with both types of digit selection) ina word-serial architecture. When compared with conventional radix-2(redundant and non-redundant) architectures, the radix-4 algorithms presenta significant speed up for angle calculation. For the computation of themagnitude the speed up is very slight, due to the nonconstant scale factorin the radix-4 algorithm.