On the Fixed-Point Accuracy Analysis and Optimization of FFT Units with CORDIC Multipliers

Abstract

Fixed-point Fast Fourier Transform (FFT) units are widely used in digital communication systems. The twiddle multipliers required for realizing large FFTs are typically implemented with the Coordinate Rotation Digital Computer (CORDIC) algorithm to restrict memory requirements. Recent approaches aiming to optimize the bit-widths of FFT units while satisfying a given maximum bound on Mean-Square-Error (MSE) mostly focus on the architectures with integer multipliers. They ignore the quantization error of coefficients, disabling them to analyze the exact error defined as the difference between the fixed-point circuit and the reference floating-point model. This paper presents an efficient analysis of MSE as well as an optimization algorithm for CORDIC-based FFT units, which is applicable to other Linear-Time-Invariant (LTI) circuits as well.