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 .
The secondary black hole interacts and becomes coplanar with the accretion disk around the primary , inspiraling toward their mass center due to the loss of the orbit angular momentum to the disk mass outside the orbit of the secondary and/or to the gravitational radiation .
The binary black holes finally merge and form a more massive ( post-merged ) black hole at center .
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 , which increases with time when the loss of the orbit angular momentum via gravitational radiation becomes dominated .
When the supermassive black holes merge , inner accretion disk disappears and the gap becomes a big hole of about several hundreds of Schwarzschild radius in the vicinity of the post-merged supermassive black hole , 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 , which has an interruption time scale \sim 1 { Myr } .
We showed that the orbit of the secondary in B1834+620 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 or borderline FR I/FR II radio galaxies and the detection rate of double-lobed radio sources among FRII radio sources is about one percent .