Stochastic Modeling and Analysis of PLL Phase Noise on QAM based Communication System

Phase noise in a phase-locked-loop (PLL) is unwanted and unavoidable. In this paper, we investigate the performance of high order QAM communication systems by using stochastic modeling of phase noise. The phase noise based on power spectral density is adopted for evaluation of noise effect. In this paper, four components in PLL are considered, which are reference oscillator, voltage controlled oscillator(VCO), filter, and divider. The second order active and passive low pass filters are considered in PLL. Also, by using PLL simulator, we analyze the phase noise characteristics in PLL components and investigate the performance improvement factor of each component. Consequently, we propose specification of phase noise requirement of VCO, phase detector, divider for performance requirement of high order QAM communication system.