Idle Tones Reduction in Digital Single-Bit ΣΔ Modulators

Single-bit ΣΔ modulators are prone to exhibit idle tones in stable operation. In audio applications the human hear can perceive this tonal behavior degrading the quality of the application. Classical solutions to overcome this problem are the use of dithering signals or chaotic modulators. In this work we compare these methods with the addition of a Fractional Delay FIR filter. The proposed technique is analyzed in terms of NTF modification and complexity, as well as the effectiveness of the technique in reducing high frequency idle tones; the impact on the modulator performance is also studied.