Phase-locked loop (PLL) was invented in the 1930s-1940s and then the intensive studies of the theory and practice of PLLs were carried out in classical works of Viterbi A..Lindsey W..Gardner F..Now PLLs are widely used in telecommunication and computer architectures.Various methods for analysis of phase-locked loops are well developed by engineers and are considered in many publications, but the problems of construction of adequate nonlinear models and nonlinear analysis of such models are still far from being resolved and require using special methods of phase synchronization theory [1-3].