Forced synchronization of two coupled van der Pol self-oscillators

The problem of external driving by the harmonic signal of two coupled self-oscillators is investigated. Comparison with the synchronization picture for phase oscillators is given. We discuss the configuration of periodic, two- and three-frequency regimes in the parameter space of external signal. The illustrations of three-frequency tori and resonance two-frequency tori are given. A number of significant differences from the bifurcation mechanisms for the destruction of synchronization are found compared with the case of phase oscillators.