The investigation of frequency modulation in voltage-controlled oscillator due to low frequency interference from supply voltage

This paper presents the theoretical analysis and experimental results of frequency modulation (FM) due to the electromagnetic interference (EMI) to the voltage-controlled oscillators (VCO). Physical models of the oscillator core and injected signals are implemented to precisely predict the EMI. A low frequency continuous wave is injected into a 900 MHz monolithic LC-VCO, which is implemented on a 0.18 µm CMOS process. The comparison of the results between experimental and theoretical output spectra of the VCO demonstrates that the injection induced frequency modulation can be quantificationally predicted.