  We propose a flexible scheme based on three coupled optical microcavities
which permits to achieve stable oscillations in the microwave range, the
frequency of which depends only on the cavity coupling rates. We find the
different dynamical regimes (soft and hard excitation) to affect the
oscillation intensity but not their period. This configuration may permit to
implement compact hyper-parametric sources on an integrated optical circuit,
with interesting applications in communications, sensing and metrology.
