The results of numerical simulation of self-oscillations in a two-stage ring oscillator with active cells of Van der Pol are presented. It is shown that for large exceedances of generation threshold in a system with identical cells, non-uniform spatial distribution of amplitudes of self-oscillations is observed.

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.

Self-oscillations in the system oscillating in discrete time and being under the influence of an external harmonious signal are investigated. As an object of researches the option of discrete map of the oscillator of Van der Pol offered earlier by authors is brought to attention. The modes of synchronous self-oscillations are analysed by means of methods of numerical experiment and harmonic balance. It is established that the effect of subharmonic synchronization in discrete time can be realized at any relation of frequencies of synchronized self-oscillations and the synchronizing signal.