A model of self-oscillating system with a differential equation of motion of fractional order under the action of external harmonic signal is proposed. Solutions of equation of motion which correspond to the regime of steady-state synchronized oscillations and the regime of beats near the synchronization band are obtained in the quasiharmonic approximation. The amplitude frequency and phase-frequency characteristics of synchronization of fractional Van-der-Pol oscillator are analyzed. An analogy between the generator with a fractional feedback circuit and the generator with delayed feedback is established.

A model of oscillation circuit containing a nonlinear fractal component of capacity is proposed. The differential equation of motion of fractional order for forced oscillations under the action of an external signal is obtained. An approximate analytical solution of the equation of motion is conducted by methods of equivalent linearization and slowly varying amplitudes. The amplitude-frequency and phase response of fractional oscillator with cubic nonlinearity are analyzed.