This is a Cloverleaf Antenna designed to sustain the reliability of the transmitter in difficult environments. They help mitigate dBi loss from reflections as the polarization does not change when waves reflect off surfaces. These antennas feature RP-SMA connectors and operate within the 2.4/5.8GHz frequency range.
4-leaf polarized antenna helps reject "multipath interference" which is a common problem with dipole antennas and significantly increase transmission range. The newest antenna has reinforcement around the clover leaf base for preventing unwanted damage, and now new cover (top piece only but is firm enough and keep weight light) is added to the package to protect antenna wires when installed on drones.