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 coordinates (for instance y) attains a target value t (in contrast to the value 0, as in standard vectoring). The main problem in the algorithm 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 convergence. We present a scheme that overcomes this and in which the implementation consists of a standard CORDIC module plus a module to determine the direction of rotation. This improves over a previous proposal in which more complex iterations are introduced as part of the CORDIC algorithm. Moreover, an error analysis is performed to determine the datapath width required for convergence. Since this width is large, we consider also the characteristics of the algorithm for a narrower datapath.