CORDIC VECTORING WITH ARBITRARY TARGET VALUE

The computation of additional functions in the CORDIC module increases its flexibility. We consider here the extension of the vectoring mode (angle calculation) so that the vector is rotated until one of the co ordinates (for instance y) attains a target value t (in contrast to th e value 0, as in standard vectoring). The main problem in the algorith m is that the modulus of the vector is scaled in each CORDIC iteration so that a direct comparison of y[j] with t does not assure convergenc e. We present a scheme that overcomes this and in which the implementa tion consists of a standard CORDIC module plus a module to determine t he direction of rotation. This improves over a previous proposal in wh ich more complex iterations are introduced as part of the CORDIC algor ithm. Moreover, an error analysis is performed to determine the datapa th width required for convergence. Since this width is large, we consi der also the characteristics of the algorithm for a narrower datapath.