Designs of angle-rotation in digital frequency synthesizer/mixer using multi-stage architectures

Abstract

The key operation of the quadrature digital frequency synthesizer/mixer (QDFS/M) in many communication systems is the rotation of an input vector in the complex plane. In this paper, we propose three multi-stage architectures for the design of the angle rotation in QDFS/M, targeting for different precision requirements. The rotation is decomposed into three sub-rotations, each implemented by ROM-based multiplicationaddition, linear approximation, or CORDIC operations. The major design consideration is to choose the proper architecture for a particular precision so that we can reduce the size of the required look-up table (LUT) and the bit widths of the corresponding arithmetic operations. Implementation results of various bit accuracies show that the best design choice depends on the desired precision.

Low-complexity rotators for the FFT using base-3 signed stages

“…Other CORDIC-based methods that consist of a cascade of micro-rotations have also been proposed [7], [8]. For instance, the redundant CORDIC algorithm [7] introduces a redundant phase representation, which removes long carry chains, leading to lower latency.…”