A fully parallel approximate CORDIC design

Abstract

This paper proposes a new approximate scheme for a coordinate rotation digital computer (CORDIC) design; this scheme is based on modifying the existing Para-CORDIC architecture with multiple approximations. These approximations make possible a relaxation of the CORDIC algorithm itself, such that a fully parallel approximate CORDIC (FPAX-CORDIC) scheme is designed. This scheme avoids the memory register of Para-CORDIC and makes fully parallel the generation of the rotation direction. A comprehensive analysis and the evaluation of the error introduced by the approximations together with different circuit-related metrics are pursued using HSPICE as simulation tool. The error analysis of this paper combines existing figures of merit for approximate computing (such as the Mean Error Distance (MED)) with CORDIC-specific parameters; a good agreement between expected and simulated error values is found. As an application to image processing, the Discrete Cosine Transformation (DCT) is investigated by utilizing the proposed approximate FPAX-CORDIC architecture with different accuracy requirements. The results confirm the viability of the proposed scheme.