Implementation of numerically controlled oscilator that uses De Moivre identity and trigonometric relations

摘要

Due to stability and controllability properties, table-based structures are preferred in numerically controlled oscillators which have important roles in digital communication systems. This work proposes a circuit that uses De Moivre and sum of angles trigonometric identities, combining a typical table driven by angle increments and De Moivre oscillator output, consequently generating more precise/accurate output with less memory requirement. Output samples of a constant frequency De Moivre oscillator are used in interpolation of intermediate values using the table, and since the table is driven by the accumulator, frequency controlled sine/cosine signal pair is obtained. Simulation results and spectrum characteristics are presented and the applicability of the method is demonstrated.