An antenna includes a ground plane, a dielectric, and an active radiating element. The dielectric is disposed on the ground plane, and the active radiating element is embedded in the dielectric for transmitting and/or receiving an RF signal. The antenna also includes a feeding element and a passive radiating element. The feeding element extends into the dielectric and is electrically coupled to the active radiating element. The passive radiating element is disposed on the ground plane and surrounds a periphery of the dielectric for perturbating the RF signal. The ground plane has a plurality of edges. At least one of the edges extends as a curvilinear lip. The curvilinear lip extends in a direction opposite the passive radiating element for directing the RF signal and for preventing abrupt discontinuity of the RF signal.