Modified virtually scaling-free adaptive CORDIC rotator algorithm and architecture

In this paper, we proposed a novel Coordinate Rotation Digital Computer (CORDIC) rotator algorithm that converges to the final target angle by adaptively executing appropriate iteration steps while keeping the scale factor virtually constant and completely predictable. The new feature of our scheme is that, depending on the input angle, the scale factor can assume only two values, viz., 1 and 1/√2, and it is independent of the number of executed iterations, nature of iterations, and word length. In this algorithm, compared to the conventional CORDIC, a reduction of 50% iteration is achieved on an average without compromising the accuracy. The adaptive selection of the appropriate iteration step is predicted from the binary representation of the target angle, and no further arithmetic computation in the angle approximation datapath is required. The convergence range of the proposed CORDIC rotator is spanned over the entire coordinate space. The new CORDIC rotator requires 22% less adders and 53% less registers compared to that of the conventional CORDIC. The synthesized cell area of the proposed CORDIC rotator core is 0.7 mm² and its power dissipation is 7 mW in IHP in-house 0.25-μm BiCMOS technology.