A particle emitter was a component of Starfleet vessels, located in the middle of the navigational deflector. It was used notably on Sovereign-class starships.

In April 2063, the Borg began to construct an interplexing beacon on the USS Enterprise-E's deflector to contact reinforcements from the Delta Quadrant. While assessing the Borg's actions in environmental suits, Captain Jean-Luc Picard told Worf and Hawk that it looked like the Borg were placing the beacon on top of the Enterprise's particle emitter. (Star Trek: First Contact)