  The activity of active galaxy may be triggered by the merge of galaxies and
present-day galaxies are probably the product of successive minor mergers. The
frequent galactic merges at high redshift imply that active galaxy harbors
supermassive unequal-mass binary black holes in its center at least once during
its life time. In this paper, we showed that the recently discovered
double-lobed FR II radio galaxies are the remnants of such supermassive binary
black holes. The inspiraling secondary black hole opens a gap in the accretion
disk and removes the inner accretion disk when it merges into the primary black
hole, leaving a big hole of about several hundreds of Schwarzschild radius in
the vicinity of the post-merged supermassive black hole and leading to an
interruption of jet formation. When the outer accretion disk slowly refills the
big hole on a viscous time scale, the jet formation restarts and the
interaction of the recurrent jets and the inter-galactic medium forms a
secondary pair of lobes. We applied the model to a particular double-lobed
radio source B1834+620 and showed that the orbit of the secondary is elliptical
with a typical eccentricity $e \simeq 0.68$ and the mass ratio $q$ of the
secondary and the primary is $0.01 \la q \la 0.4$. The accretion disk is a
standard $\alpha$-disk with $0.01 \la \alpha \la 0.04$ and the ratio of disk
half height $H$ and radius $r$ is $\delta \simeq 0.01$. The model predicates
that double-lobed radio structure forms only in FR II radio galaxies.
