The antigraviton emitter was a technology conceived of by Damar in 2374, in an effort to bring down the field of self-replicating mines which had been deployed at the entrance to the Bajoran wormhole.
Damar's plan operated by reconfiguring Deep Space 9's deflector field emitter and refocusing the emitters, essentially transforming the deflector array into an antigraviton emitter. The mines would then be isolated in an antigraviton beam, preventing them from replacing themselves. Despite an attempt by an underground resistance movement aboard the station to sabotage the plan, the Dominion was successful in destroying the minefield. (DS9: "Behind the Lines", "Favor the Bold", "Sacrifice of Angels")