The R5-D4 astromech droid, which was malfunctioning, has an antenna.
Sensory Appendages (Antennae): Certain species, like the Sleeper (a crustacean from Dathomir), possessed long, thin sensory appendages called antennae on their heads. It was believed that the antenna surgically implanted in Aurra Sing's head gave her the ability to sense fear in those she fought. Furthermore, the OG-9 homing spider droid was built with a pair of comlink antennae, and the NR-N99 Persuader-class droid enforcer also utilized two communication antennae. The R5 series astromech droid was designed to include an antenna mounted on its dome as well.
