The phase-locked loop with squarer is a classical phase-locked loop (PLL) based carrier recovery circuit. Simulation of the loop is nontrivial task, because of high-frequency properties of considered signals. Simulation in space of signals' phases allows one to overcome these difficulties, but it is required to compute phase detector characteristic. In this paper for various waveforms of high-frequency signals new classes of phase detector characteristics are computed for the first time. The problems of rigorous mathematical analysis of the control signal of voltage-controlled oscillator are discussed. Nonlinear model of PLL with squarer is constructed.