  Variability of active galactic nuclei is not well understood. One possible
explanation is existence of supermassive binary black holes (SMBBH) in their
centres. It is expected that major mergers are common in the Universe. It is
expected that each supermassive black hole of every galaxy eventually finish as
a SMBBH system in the core of newly formed galaxy. Here we model the emission
line profiles of active galactic nuclei (AGN) assuming that the flux and
emission line shapes variation are induced by supermassive binary black hole
systems (SMBBH). We assume that accreting gas inside of circumbinary (CB) disk
is photo ionized by mini accretion disk emission around each SMBBH. We
calculate variations of emission line flux, shifts and shapes for different
parameters of SMBBH orbits. We consider cases with different masses and
inclinations for circular orbits and measure the effect to the shape of
emission line profiles and flux variability.
