Digital delta-sigma modulators applied in fractional-N frequency synthesizers suffer from spurious tones which undermine the synthesizer's spectral integrity. Major conventional solutions include initial condition setup, structural modification, and dithering. For the first one the effectiveness is limited, while for the latter two, extra design effort and hardware overhead are required. In this paper, we propose a novel dithering method with simple implementation and no hardware overhead while achieving effective spur elimination. This method is implemented on MASH and single-loop DDSMs. Simulation results compared with conventional solutions prove its effectiveness.
