VCO phase noise and sideband spurs due to substrate noise generated by on-chip digital circuits

This paper presents the effects of noise generated by realistic digital circuits on RF voltage controlled oscillators (VCO) integrated in the same silicon die. The digital noise is coupled through the common substrate and generates both phase noise and sideband spurs at the VCO output. The noise coupling and impact mechanisms, and their dependence on the VCO operating conditions (control voltage, gain and bias current) are investigated